C2 2.7 cabrios are quite rare. A member on here called Roddez has a cirrius blue chrome bumpered one.
I know of a lachs silver with red leather one in Croydon which is the original press car and the first ever Alpina convertible made in either LHD or RHD! I have tried to buy it a couple of times but he's reluctant to let it go! It just sits on his drive under a tarpaulin!
The was also a white one with chrome bumpers for sale recently, that was in Epsom.
As for trim, any original E30 leather trim is very hard to find now in nice presentable condition so its a case of watching and waiting. Other than that, a high quality retrim done to look as close to OEM as possible is the only other option.
You complete grey bubble leather Motorsport cab trim (which is totaly wrong for your car) in nice condition is worth a fair bit and would certainly give you enough £ to buy another normal leather trim for your cabrio, or a big chunk of £ towards a top quality retrim.
By the way, if you need any info on E30 Alpina stuff, drop me a PM as i have alot of info on them.