V60i Slim replacement battery

I need to replace my v60i Slim Li-Ion battery. The current battery is a
Motorola SNN5722A. I would like the largest capacity, longest lived battery
without changing the form factor from Slim. I would like the battery to
react to fast car charges at least as well as the Motorola batteries.

1) Are 3rd party batteries OK and any recommendations on brands.

2) Any recommendations on cheap sources of good fresh batteries.

Thanks,

Joe M