CR-2032 lithium button cell -- you can buy these at Radio Shack, Target, Staples, etc.

CR2032 batteries are common ones for many electronics and can be found at the jewelry counter in any discount or drug store for $2-$3.. Directions to replace are HERE. Replacement requires disassembling the computer so be be sure to follow all safety directions.

For $2.39 including shipping, I bought 5 of the CR2032 on eBay from a USA seller.  :emotion-2:  Needed it to test out an old Sharp Electronic Organizer that took 3 of them.

Thanks for all your answers.  I know I have to take everything apart to safely change out the CMOS battery.  Hopefully that will go well.  The last time I serviced the laptop I almost damaged the CPU fan, jerked one of the pin wires off the power connector but managed to seat it back into the connector after fiddling with it, like threading a needle.

At least the CMOS battery on this model is right below the keyboard, on top of the system board.