My T/D 90 had one of the short depth ones appropriate to the radio cassettes of the nineties. I now have a radio cd and thus tried to find one of the more modern full depth surrounds at numerous auto jumbles. I "stalked" a second hand one on Ebay but at £15 plus postage thought too much for a pig in a poke. An Ebay shop has some for sale for just under £25 plus postage.
Fed up I tried my Local Main Dealer.
Astonishment - "£18 sir"
Even greater astonishment - "We have one in stock"
Just goes to show (or not!)