Volks,
'86 weekender with 100k miles

Under the van, in the back seat area, are 2 metal "T" fittings that (I presume) supply the rear heater core with coolant. One is leaking and I can't seem to find them for sale anywhere. Are these one of those DIY pieces that aren't for sale anymore, or am I just not a very good parts searcher?
If they are a DIY piece, can someone point me in the direction of a website which gives good info on them?
Thanks,
Joel in Philly