Have you looked at Charlotte pipe fittings for this as they have a good selection of pipe fittings?
I'm still having trouble finding this and when I look at the OTB revit fitting families, like I want to start with one of those to create the LTTY fitting, there are a million parameters in the family, it's insane. I can find a double LTT fitting but not a single! What is up with that?! And why can't I just make one side of the fitting disappear like I can on the other fittings? This is driving me crazy.
Is this any use if you change the materials?