I've got a 97 R11R, and I'd feel safer with the wifey back there dozing if a sudden acceleration didn't risk spitting her out the back like a watermelon seed. Seems Reynolds racks are no longer made, though sometimes available in the Flea Market. And hard trunks are a fitment issue.
Anyone tried a Sargent backrest like this?
Seems like a backrest and rack at a reasonable price from a reputable vendor...
if you have the bmw rear rack, there is a passenger seat adapter that slides right in. You can use it with the stock (or other) saddle. Got mine off of eBay for cheap.
You could try Pirates Lair - http://piratesk12site.net/
I have their backrest for my R1150R and it is awesome! I don't see the R11R listed but you could check with them.