I made one from a piece of scrap steel. I put a hole in one end and a loop of sturdy wire thru it.
I place the loop of the wire around the ball knob of the vise handle. One end or the other of the vise handle seems to always come up in a position to take it securely.

Makes getting that thing back together again easier but it's still a pain to assemble..

Seems like I use that on the Flues model Ithaca as well. Same set up.