HeX-Cheat:
Edit the mission files with a Hex editor and make the changes detailed in the table below to increase the number of credits you have to 800. This should be plenty as if you were to spend more you would be too heavily weighed down and you'd lose lots of action points.

File Starting Offset Type:

1 Hex 2309 20 03 20 03 20 03 20 03
2 Hex 2309 20 03 20 03 20 03 20 03 20 03 20 03 20 03
3 Hex 2309 20 03 20 03 20 03 20 03 20 03 20 03 20 03
4 Hex 2309 20 03 20 03 20 03 20 03 20 03 20 03 20 03
5 Hex 2309 20 03 20 03 20 03 20 03 20 03 20 03 20 03