I checked with our Harris shop yesterday; if it's a Li-Ion battery (or LiP), it should charge on the Harris charger. So I bought one of the 4100 mAh jobs. We'll see....
Follow up....
I ordered my battery from TAC1 Systems:
Harris Unity XG-100P Lithium Polymer Battery - 4100mAh
Ultra hi-cap 4100mAh Lithium Polymer battery for Harris Unity XG-100P 2-way radios. Highest runtimes for mission critical comms. Extended warranty. Fast shipping.
store.tac1systems.com
Works like a charm, keeps my radio going for over a day (using the 80/15/5 formula), and charges just fine in both of my Harris chargers (the older model as well as the low-profile one that came with the XG100P).
Just a little FYI. The wvbandcoms.com/ 4100 lithium battery ($85) will charge just fine in a Harris lithium charger (104560-016). Makes for a pretty economical battery solution.
Picture here
Have you used this one in an XG100P?