Latest Update:

The mysterious and elusive v-block has a brand name: Center-It.

After 4 hardware stores I figured it out. HF has them in the catalog,
but not the local store. Ditto on Wick's and AS&S catalogs.

But for $20 (w/ s & h) I'm seroiusly considering dragging out the table
saw and making one out of wood.

Veedubber also suggested low-temp brazing rods with the MAPP torch. A
quick Google led to several sites of guys brazing bike frames with
1/16" solid brass rods, stanadrd Mapp/air torches and regular old boric
acid as flux.

I think I may etch the zinc off a few chunks of conduit and give it a
try in the next few days.

Stay tuned.

Harry