With the 59 series guns no longer in production there isn't a lot of aftermarket support. I'm after magazine holsters for modern guns that will accommodate 59 series magazines. I can already rule out Glock magazines, they're too wide. I don't own any double stack M&P handguns, etc. to compare.

Are you looking for a pouch for CCW or competition?

Double stack steel mags are much like each other: M59 and SIG and Beretta leather pouches will work just fine. Yup, Glocks are much bulkier.

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Red Nichols The Holstorian

Ultimately, I'm after a magazine handcuff combination holster, which are usually hard plastic.

Try this, size “Group 4.”

Model 573 Open Top Magazine and HandCuff Pouch - The Safariland Group

Or this:

Combo Pouch

There are many others, but I did not want to look them all up for you.

I'll add to post #3 that suggested 59 magazines and Sig and Beretta magazines have similar dimensions: add the Taurus PT92/99, the Browning Hi-Power, Star Model 30 and the Ruger P-89/P-95 magazines. The length is different and the actual magazine catch is quite different, but the front to back and width dimensions are all almost exactly the same as the Smith & Wesson 59, 659, 5906 and all 1-2-3rd Generation S&W double stack 9mm magazines.

Glock magazines, always made of plastic and not steel are always dimensionally larger. Find something that says it fits the Beretta 92 and you'll almost surely have a unit that holds a 5906 magazine properly.