I bought a box of 200 assorted springs at Menard's and found one in there that was the same size as the factory trigger return spring. I bent and clipped the ends and installed it. Trigger pull went from 5.5 down to 3.5 pounds. After 2000 rounds, it's still working fine.
For any Canadian PPQ owners looking to do the 3.5lbs TRS mod if you order the spring from McMaster, as listed in LANZER's post, it ships from Mississauga. I tried the 200 assorted spring pack from Princess Auto and the trigger pull was about 2lbs. Too low for IPSC. The McMaster spring is just right and works awesome.