After destroying 2, I'll never take one off again unless it's already cracked and I know it's going in the garbage anyway.
You probably won't find a new old stock one, but you can get the new model if you can tolerate your rebuild not being accurately vintage.
Aqua Lung Exhaust Tee for Conshelf XIV 1019-19
I have put a couple of them on XIVs.
The other alternative is to find a cheap 1085 with a scuffed up face plate that nobody wants for sale on EBay and use just the box with exhaust t attached.
VINTAGE US DIVERS AQUALUNG AQUARIUS SINGLE HOSE SCUBA DIVE REGULATOR | eBay