With these batteries getting older now it is inevetable that they will evenually fail.
I've remoddled a design that will fit straight into a Stalker LR and provide room inside to mount DC to DC converter (7.5-8V) is what I recomend to use as out put voltage.
I used Spade Plugs as terminals (after bending the top part)
I've printed in in PLA and it seems to be holding up fine.