3M has a couple different types of double-sided plates. Their Viking S2 is a
thin (5 mil), smooth, double-sided plate, pin-bar punch for use primarily on
duplicator presses - designed for short runs (<25,000). The Viking G2 is a
grained plate for medium runs (~100,000).
The S2 plate 11"x18.5" (5 mil) costs $2.01.
The G2 plate (same size) is about $2.40.
Compared to a single-sided plate, similar size -- 12"x15.5" (8 mil) for $2.82
The contact at 3M is Jan (don't know her last name) (800) 328-1303
FYI, we are currently working with a newspaper in Montana that is
considering converting to direct-to-plate plastic plates. This would
eliminate all their development chemistry, ideally without sacraficing
quality. Stay tuned.