Allan,

This happened to me and a friend of mine recently. While we have yet to do
the repair here is what I found out:

1. The expansion tanks are not under pressure so repair is possible
2. Here are some suggestions that were given:
    JB Weld SHould work
    replace nipple with small tube or piping - jb weld or use other method
to install

Like I said we haven't gottne to it yet ourselves but as I understand it is
repairable. I couldn't find any sources for new expansion tanks either.
Might find them used on the Samba or Ebay if you choose to go that route.

Good luck.

--
Thanks,

Jeff
'90 Carat (Grover)
'86 (We call this one Parts)
'78 Bus (Melissa) Patty's Bus