Thank you canderson! There are several batteries to choose on the site you suggested along with other sites. Do you know what the mAH OEM for this battery is? I've seen them offered from 700mAH to 920mAH for the 1535TM.
I believe the 'standard' for yours is the 800mAH. The higher ones, as I recall, were for the GO 1535 that included Live traffic services since the cell modem was a bit more of a power sucker. Not sure why they're showing other than 800mAH for yours. Of course, if you find greater capacity in a pack that will fit, nothing wrong with that, either.