I bought a replacement set of map pockets through eBay, and reinforced them before installation with a length of 1/8" x 1/2" steel, drilled at 1/2" intervals to accept something like a 1/8" (10-40?) bolt and nut.

Step by step:

a) Drill the steel.
b) Bend the steel to fit inside the top lip of the map pocket.
c) Because you'll have "bent" some of the holes, run the drill through the holes again.
d) Clamp the steel in place, and drill a hole at each end of the map pocket.
e) Bolt the steel to the map pocket through those two holes.
f) Drill the rest of the holes in the map pocket.
g) Dismount the steel. Clean up the holes in the plastic if necessary.
h) Epoxy the steel to the map pocket.
i) Install bolts in each hole. I used a thin flat washer under the bolt head, and thinking that a little epoxy in the threads would act like threadlock, installed the bolts right away without waiting for the epoxy to cure.

Let it dry. You might use a Dremel to round the bottom threads of the bolts. Paint if you wish.

I'm sure these map pockets will survive a nuclear attack.
--
David Brick, Santa Cruz CA, 1988 245