If you don't find something at mondolincafe, some of the guys from "Mass Street Music" (Lawrence KS) have seemed to include quite a concentration of mando people at Winfield. The store does appear to be pretty heavily into decent older instruments, so someone there might be able to provide some information - if you can find the right one or two of them.

They usaully have camped near the main entrance, roughly between the ticket booth and Billigan's Island.

Note that I've never interrogated any of them (at least not with the bright light and a rubber hose) to see if they really know anything. They do seem to be at least one of the most active dealers in "used instruments" that I've seen in the region, although there may be comparable ones in Big D or nearby.

Of course you'd have to wait for next September to catch them there, but it's only about 550 miles (each way) to take a run up there and talk to 'em. (You might want to call, or drop them an email first?)

John