I went to the local Batteries Plus store this morning and bought 4 CR123A batteries. They spot-welded the tabs on for me for free while I waited. The guys were all my age or older. (geezers!) The spot-welding machine looked quite serious and well-used.

It appeared to me that the shop assembles battery packs for lots of different items and I'd expect that if I just took them the packs from my PLB that they could fab up replacement packs quickly and for a very nominal charge. I'll hold that thought in the event that I fail at doing it myself.

I thought I'd post this idea in case someone else wants to refresh their battery packs for less cost though trading off manufacturer final testing in the process.