I live in a place where most of you would be horrified lol. I am a germophobe, but have had to modify my habit living here :P
I have just carried my babies until they could sit safely, and then even my most 'mouthy' child has never, ever put their mouth on/licked the trolley.
If you really don't think you could cope with the thoughts of what might happen 'if' then yes you should get one, but to me the risk was low. There are plenty of places to get germs.