"Foolestroupe's well-meant suggestions are almost all completely wrong"

So True! Thank you Jack! :-)

We'll try again then - I enjoy being helpful... :-P

"A porous material won't necessarily be a good enough barrier. "

As long as you have no allergy to plastic materials, you could completely replace the straps with such materials, or try sealing the material with various types of plastic - one suggestion is the stuff you can get in a can from a hardware store to dip the handles of pliers etc. Not being cruel, I will refrain from suggesting to use the whole instrument....