Micro ATX PSUs are difficult to find. I know as i have to try and replace the Tiny ones that are no failing left, right and centre. Two solutions. 1) Buy from USA for best part of $100 or 2) New case and (at least) 350 watt PSU.
Personally with a P2.4 and that G Card i would get a new 400 watt PSU first. Micro ATX cases can't be (easily) modified to take a newer PSU so i would look at a new case and PSU.