Custom Products makes aftermarket triggers for the Invert Mini (and numerous other paintball guns).   There is one to match any color of Mini you might have and two styles to match your preferece.  The styles are know as the Slingblade and the Rake.

The follow excerpt is from the Custom Products website:

Upgrade your game with the new CP Invert Mini Roller Bearing Trigger. The CP Trigger uses spring return instead of the stock magnet return. This provides a much more consistent and smooth pull and return than the stock trigger. Also, the trigger uses a precision roller bearing to ensure the smoothest trigger pull you can have.