I got some from "pilgrim18" on eBay, a selection for £3.50 + 50p p&p. He advertises it regularly.
Don't know if you've done this job before but after a couple of attempts at cutting and fitting the VERY narrow bits in the channels where the back closes, on an SLR, I gave up with the adhesive-backed! I just cut some non-adhesive strips slightly wider and pushed it home, it stays there all by itself. It's near-impossible to guide the adhesive-backed stuff into the narrow channel without it sticking to the sides :-( With hindsight I maybe should have laid it in the channel with the backing still on and peeled it off in-situ, but I never tried that idea. Anyone have any tips on how it should be done?