the web of my hand rubs raw after a few mags.  Are there any grips that cover the beaver tail or otherwise offer relief?

I did two things with my PPKs to avoid this:
1) lightly sand the edges of the beaver tail down - this helps the most.  All you need to do is round the edges a little.
2) get wood grips - some will widen the grip a little and add to the back strap and beaver tail to take the edge off for you, but they are much better than the factory plastic grips that offer no protection from the back strap and beaver tail.

I had the same issue with my PPK and a nice set of tulipwood grips solved it very nicely for me. I no longer have two parallel grooves scarring the back of my thumb joint. They are just enough wider than the plastic grips to flatten the area around my thumb joint so that the slide bite doesn't happen any more, not to mention that the tulipwood looks great against my stainless PPK.