Your idea will do the trick. I did that with the battery rubber (came out in less than 2 months).
As for the "original parts" I couldn't find anything. All that I did was
the whole bottom part, but changing the whole bottom side for a rubber foot is kind of a waste of money if you manage to improvise.
Note: don't know where you live, so you might not be able to order from that site (or due to high transportation costs if you live outside EU).