Just tossing it out there.
The Yamasaki 90's seem to have a similar track record to the old Angulon 90's. Sure you don't want to give the latter a try?
Another option is the old tiny 88mm B&L Wide-Angle. It's a double-gauss similar to the Wide-Field Ektar. I have one that's lightly coated. Being only four air-glass surfaces single coating works well.
Neither of these will preform like your excellent 90mm Nikkor-SW but this is a trade-off for size/weight/cost.