Where can I get reliable offline drivers for a PS3 Controller?

You may want to take a look at XInput Wrapper for DS3. It does turn your PS3 controller into an XInput device so you can map the buttons basically in any application/game supporting the XInput library. Combined with Pokopom's XInput Pad Plugin you should be very fine. I haven't tried it for myself but I've heard from quite a few people that it works very well.

I recommend installing the MotionJoy drivers and using Better DS3 to actually manage the controller:

Better DS3 has a simpler, better interface but does all the things Motionjoy's DS3 tool does. You still have to install the drivers from MotionJoy but Better DS3 can be used offline. Once you install the drivers you can simply use Better DS3 at all times to replace the DS3tool configuration. Also, no nasty ads in Better DS3, unlike Motionjoy's solution.

Since you're using the motionjoy drivers, your PS3 controller can be used without running anything like a batch file every time you plug it in/turn it on. It sounds like Better DS3 even handles Bluetooth pairing so you should never need to launch MotionJoy or connect to the internet after downloading.