Remote Pushbutton

I would like to use a wireless relay to put in a remote pushbutton to open an automatic door. The relay card pairs that I have used before are out of stock until June, so I am wondering what other good basic options I have.
A keyfob is not an option here as the customer has a paranoia about anything with batteries that he may have to replace.
I also would prefer not to connect to a wireless network , I would just like two devices that talk to each other.

Unfortunately we do not have any alternative solutions at this time if you are not able to use a key fob.