This is for an OEM, not a knockoff generic, Treo battery.
It is $31.56 from Amazon, but only $10,43 shipped from Eforcity, a 3rd party vendor on Amazon’s site. Just be sure to add the battery from Eforcity to get the correct price!
3rd party vendor purchases are fully protected via Amazon’s A-to-Z guarantee.
Palm Treo 650/700p/700w/700wx OEM Battery Linky
If you do pick up this handy spare battery, you may also want to consider getting the Palm spare battery charger, currently just $19.99 shipped directly from Palm. The charger is compatible with the Treo 650/680/700p/700w/700wx/750/755p. (I used it extensively before switching to the incompatible Centro…)