A/C O-ring sealant?

[Dave C]

There is a leaking seal in my A/C system, 89 Audi 100 and a new seal is
apparently not available.  This seal is an irregular shaped O-ring between
the two halves of the manifold.  The manifold is the rectangular block
attached to the driver side of the compressor which the high and low
pressure hoses screw on to.  There are five bolts holding these two halves
together.  Three of the bolts also attach it to the compressor. In the
process of compressor replacement I removed all five bolts before realizing
two of them should >not< have been disturbed, and I broke the seal between
the manifold halves.  All of the parts sources I know say this seal is NLA.
It is not shown on the FA.  The only thing available new would be the entire
manifold assembly for $650. FA shows the manifold as 034 298 013C "Union
with charge valve and securing parts".

So I recharged the system and now there's a lot of oil dripping from the
manifold.  I suppose I could disassemble it, clean off the oil, smear some
special goop onto it, reassemble and hope for the best.  Is there a source
for the new seal?  Is there some sort of goop or sealant I could smear onto
the old O-ring that would seal it properly?  What type of goop would be
best?  Any BTDT help would be most appreciated.
thanks,
Dave C