I purchased one of those cheap spotwelders from Ebay search: "Portable Battery Nickel Sheet Spot Welder PCB Circuit Board With Battery Set USA" for $25 and it works pretty well. Dont press too hard or it wont weld the nickle strip to batteries that well.
You'll have to disconnect the cables from the PCB, slide them through the correct holes in the body print, then reconnect them. It's a pretty tight fit, so your board needs to be very square to the battery.
After a little cleanup with an exacto knife, I glued the two halves together and used tape to hold it in place while it set.
Since it's a nameless chinese brand, I embossed the front with the funny Ebay description.

Creality

CR-10

No

Yes

.2

100

I used supports wtih roof enabled in Cura at 15% infill. 60mm/s = 3.5 hours for the body and 1 hour for the back.