Thanks for the self-help suggestion, and the product link (my search-terms must indeed have been inadequate)…

Thanks so much for the comments.

After viewing in-stock battery clips, did get the impression it was custom.

Interesting suggestions re: part from a broken one, foil /paperclip, and shape-your-own (not set up to re-plate).

Since it’s summer here, do have a while to explore options before the next heating season.

PS For future reference, does this sort of exposed PCB trace (pad?) used for electrical connection take solder well?