Llama4x4 (Rough Country) can also supply a 12" travel damper with eyes on both ends or at least they were about a year ago. I haven't seen Llama advertise it, but one of my house mates got a pair of them. IIRC they were intended origionally for a large america pickup and Llama had them with the intention of using with the max-traction setup as the should be a higher rate of dampeing than procomps.
Probably worth giving David at Llama a call and see if he still supplies them.