STI mags should be okay.
A lesson I learned on mags for my .45:
Store "A" had a bunch of mags for sale. The .45 mags went for under $10 a piece. I bought 10. By the time that I sorted out the good from the bad, cannibalized a couple, I had one good mag that was dependable. Spent a little under $100 for one stinking mag. My money would have been better spent on a couple of mags costing $35 each.
The mag is the critical part of any semi-auto. If it breaks, your firearm is a single shot (at best).
Don't scrimp on the mag. Buy the quality and piece-of-mind. It is well worth it.
(I've spent over $75 for one mag for my H&K PSP P7)
"A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed."
Life Member NRA
Life Member NAHC
Former President of the ECPT (Eifel Combat Pistol Team)