I have the HTC TyYn II and although its a fantastic PDA, with business use I never have enough bettery life.
I have purchased a new emergency charger from a company called battech internation that are a UK battery company.
After testing this external battery i have found it a valable device....her it is if anyone else has had simular problems with needing constand portable power.
Battech Store: Battech Chargers