You can buy some
such as these. They have strands of metal woven into them. Mobile phone screens used to be touch sensitive, but now the electronics do not detect pressure, but the presense of a finger at the surface or nearby (or other detectable object, such as a stylus).
but you might still accidentally touch the button.
and touch the button with that. Then drop the foil into a bag or bin so you don't have to touch the other side of it. I have tested this on my mobile phone. The first time it did not immediately work: I had to hold my wrapped finger against the screen, but on subsequent attempts I could tap the screen successfully. Using a piece of paper did not work.
A simpler version would be to
The simplest and least wasteful method: use your hands to operate the buttons, wash your hands afterwards.
Any other methods will just move the (potential) contamination around, so you'd have to use disposable or washable items.
Your biggest problem is not the touch sensitive button, but your (justified) fear of contracting germs.
My quick-hack for all kinds of surfaces that must be touched but aren't clean is to use the back of my hand or my finger. You can push mechanical and touch operated buttons by curling in your finger and pressing the back of a finger joint or knuckle to the button.
You might still catch some harmful germs this way, but they stay on the back of your hand until you wash them away. People usually use their fingertips whenever they touch their face (scratch an itch or rub your eyes). As long as you remember not to rub your eyes with the backside of your finger or hand, the risk of contracting harmful germs is reduced compared to pushing the button with your fingertip.
Of course, this does not eliminate the need to wash your hands. It just reduces the risk of accidently bringing harmful germs in contact with your face before you wash your hands.
An easier solution might be to just bring alcohol wipes in your pocket and wipe the button first. (the small kind that would be used before blood work or a injection).
May as well wipe them all and help everyone out.
Assuming the buttons use a body capacitance detector (as is the case with touch controlled lamp dimmers, wall switches, and smart phone screens), you can use a stylus intended for a cell phone or tablet and get the same effect -- and the business end of the stylus need never touch your skin.
Use a touch screen pen which can be used on mobiles - example is https://www.amazon.ca/LifeFan-Stylus-Precise-Double-Replacement/dp/B07FJXMMRP
Notice the wired gauze portion on the back. That works on touch screens.
Use a pomme frite.
I have only tried with hot or luke warm pommes frites but see no reason why it should not work with a cold.
You can make them at home or buy them at a shop; then keep them in a small box in a pocket. Make sure the box is tight and does not leak oil though, as pommes frites are quite oily.
You can reuse the pomme frite several times (there is no need to estimate how many times you go up and down in the elevator every day and cook before hand) so unless you plan on travelling vertically for many many times one pomme frite a day should work. If you should happen to wear out your pomme frite there is often a shop nearby (ysc may vary)* to purchase a new.
Depending on your respect for germs you might not want to eat it afterwards; but the taste should be about the same.
Finally, if you are sensitive about your health. The best thing you can do is probably taking the stairs anyway.
*)Your Size of Community
Wrap your finger in cling wrap. Discard after use.
There are gloves available that allow you to use your mobile phone while wearing gloves. They conduct enough electricity to allow "touch" sensitive (actually electric conduction sensitive) interfaces to work. The gloves are pretty cheap and available everywhere.
Here's an inexpensive version from Amazon. https://www.amazon.com/HONYAR-Gloves-Winter-Touch-Screen/dp/B07WJ4TPTZ/ref=sr_1_14?crid=27NFPMNHAV1JB&dchild=1&keywords=cell+phone+gloves&qid=1582904607&sprefix=cell+phone+glo%2Caps%2C180&sr=8-14
Do everyone a favour - bring a small bottle of hand sanitizer, and use it on the button before (or perhaps while) you press it. Clean button! Then possibly clean your hands again afterwards.
Use the point of a knife and touch it to the edge of the button where no human finger usually touches. The surface area contacting the button is extremely small, a lot smaller that the surface of your finger. Statistically speaking, if the surface area is a thousand times smaller, that's a thousand times better than using your finger.
Or use a copper wire and burn the end of it with a lighter to sterilize it afterwards.
Use your elbow, just make sure not to lick it later.
Do you have keys on you? Use those.
A pen on hand? Use the back end.