have you seen this? DUCATI 888 851 1992 BREAKING DUCATI 996 748 916 | eBay (I've no interest in the sale)
Dammit! sorry to hear that (given the rarity have you considered a frame builder?) (Edit: or maybe an ST or Monster surrogate to be adjusted)
Spurred by your reminder, I dropped the seller a line. He actually has one 851 & an 888 frame both with German docs, so a good find - thanks again. He offered them to me before putting them on eBay at the weekend, but my contact has now decided he'd prefer a complete bike, even if with a blown engine as his plan is to build a special. Doing favours for pals abroad gets complicated!!
I know of 3, ST4S non runners for sale. All in various states of decline, some with some nice goodies.