Practically any double AR mag pouch will do for a single M1A-type mag.

The older MOLLE double AR mag pouches, in woodland or desert camo, and with the adjustable bungee cord at the mouth of the pouch, instead of the non-adjustable elastic band around the middle of the pouch were/are some of my favorites.  Not too easy to come by nowadays.

This might work:https://www.entrygear.com/product.asp?id=BAE-3041.  The khaki goes pretty well with multicam.

The only issue with some double AR mag pouches is that the elastic so often used makes re-insertion of the 7-62 mag problematic.  I have found that carefully removing the elastic, and substituting an ESSTAC 7.62 KYWI solves re-insertion and retention issues, since it both grips the mag, and holds open the mouth of the pouch.  If you order from ESSTAC, ask them to include some sticky back fuzzy Velcro for each KYWI.  Each KYWI comes with male Velcro already attached to it; Add the female (fuzzy) velcro to the inside bottom of the pouch to help retain the KYWI.

I also understand that HSGI is coming out with some new pouches--with flaps--, but no idea on when.

I'd hold out until I discovered a single thickness 7.62 pouch.  Going double thickness is not the way I'd want to go.

This pouch, currently discounted (depending on color/camo scheme) is almost identical to the old MOLLE double AR-mag pouch that translated almost perfectly into a single M-14/clone pouch: http://www.tacticaltailor.com/556doublemagpouch.aspx

I have found these pouches do very well in the single 7.62 mag role, as long as the bungee cord is not drawn tight at all.  In fact, if one adds a 7.62 ESSTAC KYWI insert, and some appropriate velcro inside the pouch as a retainer for the insert, they are almost perfect.  Zero problems with extraction, and zero problems with re-insertion.  YMMV

It's not easy to find a single mag, flapped 7.62 mag pouch, but many double AR mag pouches will do.  If you want to re-insert the used mag, then definitely use a 7.62 KYWI, or perhaps some other iteration of same.

Of late, there are some other, U-shaped, kydex devices, which grip the mag at its' sides, as opposed to the KYWI's front-and-back grip.  These are similar to the items offered by, notably, HSGI, but since they are internal to the pouch, do not require any sort of shock cord.

I might make some and see how they work.  One can do that with Kydex, after all.

SCW, did you get my IM?