The rubber-back issue isn't really a dealbreaker - since just about any old N90 will have that (unless they replaced the back under warranty??)
The stuff comes off pretty easily (and it's clear, not black. Removing it leaves the black paint in place - you will lose the white program icons though).
I just took 99% isopropyl and some strips of plastic food wrap. Drip some on, and lay the plastic on to keep the alcohol from evaporating. Let is soak in, then scrub with a rough cloth. After several rounds of this, it will be gone in the areas with the most wear, and no longer sticky - just sort of a translucent matte finish - everywhere else.
I left it at that, but you can likely get it all off.
Other have used various chemicals, acetone, etc - I didn't want to remove the black paint or damage any plastic parts though.
I bought my N90s new ages ago - it still functions like new, and it was my main fashion shooter for years - lots of rolls run through it. Workhorse is the word.