Get hold of two ammunition bandoliers, cut the bottom out of one and stitch the two together, so that the bottomless one is on top of the other, retaining the top ones shoulder strap. Get the tailor to go over all the stitching to toughen it up a bit, hey presto, home made mag bandolier. Blue Peter ain't got nowt on this shizzle!!!
If you want the bandoleers that are currently issued to U.S. forces, here is a link to a good company that has them in stock. They are sold as ten-packs for about $14.95 US.
These are intended to hold 3 ten round M-16 (NATO) stripper clips per pocket, 4 pockets. By removing a line of stitching near the bottom of the pockets, a single loaded 30 round magazine can be carried in each pocket. If you use a thin cardboard insert (easily made) that surrounds the magazines, there is very little noise made when carrying two or more full bandoleers.
These bandoleers are made out of a thin linen type material, but have proven to be very tough even under hard field use.
What I use is not for Mags but for 2 boxes of 7.62 with 20 rounds in each box ,I took a M-203 cotton bandolier with is made of 2 pouches joined with cotton webbing and closed with webbing flaps and domes , Unstiched the flaps and moved then back to close over the open box , I can carry it
in the ammo pouch ,pull it out lay it on the ground and open it up on 1 flap for the 5 rounds of the M-24 ,simple and has lasted 5 years of reserve use .
To make a Bandolier for mags you could use heavy cotton drill or 420 nylon with Velcro to close the flaps.
This you could make on a home sewing machine.