Bath Mats-Oh My!

I've spent a great deal of time today looking for an eco-friendly anti-slip bath mat. You see, I currently have to constantly hold onto Henry at bathtime as it's quite slippery in our tub -- and he's growing more annoyed and independent by the second.

About a month ago, in haste, I just quickly ordered an anti-slip "jelly" bath mat and some anti-slip stickers (without my green thinking cap on). They were so incredibly smelly - had all the unsafe plastic numbers and PVC to boot. To think of Henry bathing with that plastic really kinda scared me. (I should add that he happily bathed in a plastic bathtub for several months as a little baby before I even realized what I was doing.)

Eek! And now I can't find an eco-friendly anti-slip option without all the toxic plastic stuff. I'm really at a loss here. (And since we rent I can't add any adhesives - has to be a temporary solution.) Any suggestions on PVC-free bath mats? Anyone?