Ideas Needed, 85 Vanagon Rear Suspension

Hi,
I'm usually over at the pinball group but I'm having a major issue
with hubby's vanagon (he is gone on temp duty) and I am hoping someone
here has a workable solution for our vanagon. The rear coil sping is
good but the "nub" that the coil spring fits around and that keeps it
aligned in the trailing arm has rusted/broken off.

The rest of the trailing arm, axle is all great without rust, just the
one part is bad, on both sides. The one coil actually "jumped out" of
the trailing arm which made a horrid, scary noise. I immediately
stopped and had it towed which was good because no other damage was
done. The other side, the nub is gone but the coil didn't try to
escape.

Bad news is that the nub is part of the trailing arm, not a separate
piece. Cheapest price I have found for a trailing arm is $735. each
not including labor. I imagine if I were to replace both sides the
labor will run over a thousand for taking off and reassembling the
whole rear end of the van. My mechanic says he is willing to try to
weld a piece of metal in there if I can come up with something that is
the same diameter/size as the nub.

I have searched all day for a solution and am running out of ideas.
Anyone have suggestions for what could be welded in there? Or what
else would work?

Or if someone has an alternative for the rear suspension that would
work. Could the bottom of the spring be welded or is there a way to
keep the spring in place? Any ideas are very appreciated!
Thanks,
Laura