Rarely if ever eat there, Tilly, but do need to use the facilities on a regular basis.
Rigorous hand washing is always done, and they don’t usually have doors which need opening to exit the facilities but the doors into the service stations almost always need to be opened using the handle.
And often there are coach loads of foreign tourists there too.
Rubber gloves? Full rubber suit as in jno’s link? Any other suggestions??
But then the germs are on your sleeve! Even before Covid, I always used my little finger at the very bottom of the handle to open the exit door on the basis that most/all people grab the middle of the handle.
If they aren't sold out,get some disposable latex gloves or check disability aid sites for door handle and door knob openers for those with poor dexterity.