There are a couple of alternatives.
One is to use a small NiCd pack, such as used for some cordless phones. Many of these are 3.6V, which seems to be enough to work in most Pluses. I see these everywhere for a buck or two around here.
Another option that I've wanted to try, but have not yet, is to mod the Plus to use a supercapacitor (order of a farad; just need a small number of other parts). Not quite the same as a battery, but it may hold charge for days or hopefully weeks, which might be satisfactory.
Both of these options are cheap cheap cheap, compared to getting the official replacement. As long as you don't mind the mods, these should do the trick.
One is to use a small NiCd pack, such as used for some cordless phones. Many of these are 3.6V, which seems to be enough to work in most Pluses. I see these everywhere for a buck or two around here.
Another option that I've wanted to try, but have not yet, is to mod the Plus to use a supercapacitor (order of a farad; just need a small number of other parts). Not quite the same as a battery, but it may hold charge for days or hopefully weeks, which might be satisfactory.
Both of these options are cheap cheap cheap, compared to getting the official replacement. As long as you don't mind the mods, these should do the trick.