It's good to know that Batteries Plus is treating you the way they should. I've always had good luck with them.
Keep us posted on how the battery they are ordering works out. I have a Niterider MiNewt 600 and as with anything with a battery it's just a matter of time before it goes bad. When the time comes I'll replace the battery if the price is right but at $40 I think I would replace it with a new light. It seems like lights keep getting better so I can't see spending that much to keep an old one working.