A smaller DMT plate, such as their 3" x 8" plates would work well. There are some plates made in Japan I've seen sold in various grits by JBroida and Schtoo that should do well, too. Granted, a 10" x 4" 120 grit plate sounds most excellent, but the slightly smaller plates still work great and usually cost a lot less.
"I knew you before you knew you had hands!" ~Tracey Brogan
Serenity Prayer - Calvin's Edition: For the strength to change what I can, the inability to accept what I can't, and the incapacity to know the difference. ~Bill Watterson