Maybe I've led a sheltered life. I've tried, but still can't see the utility value of an IWB magazine carrier.
About 1/3 of the upper mag body will be xposed even when carried IWB. Maybe a 'tuckable' or a 'crotch carry where the mag is accessed by unziping your fly can cover the entire magazine. Don't know.
There are a couple of clip on IWB Bianchi single stack carriers that I have tried. They now reside in my 'didn't work out' leather box. Those weren't worth a flip for IWB use but seem to do OK when carried in an inner jacket pocket or shaving kit.
'Luck to you,
Bread and Circuses don't pay the Bills.