At most drug stores you can buy mini condoms ( for your fingers) the call them " finger cotts"
They use them to protect your fingers, and also that will not contaminate other items, like pills.
They are inexpensive, and "Most Likely" your wife won't be too concerned.
They work well.
One question! If you don't put a ball in the barrel, will you get a very big balloon, on the end of the barrel, after shooting?
Merry Christmas
Old Ford