Move fast when you find one... and in that price range, unless it's in need of some work, you're not going to need to bother haggling. After missing out on, literally, a dozen units over a years time... I found one on craigslist in Grand Rapids, MI.
Here's how it played out in my instance...
~2pm .. found 1976, 13' Scamp
in Grand Rapids on Craigslist, small photos look promising
2:02pm.. talked to owner, says nothing seriously wrong with it. I tell her "I'll take it, but you have to promise me you won't sell it between now and the time I get there after driving over 600 miles to get it!!". Owner agrees, "It's yours."
2:15pm.. hitch hooked up, change of clothes packed, leaving home in our Honda Element, which has patiently been waiting to pull a 13 footer for a year now.
2:30pm.. stop at bank, withdraw $2,000 (a coincidence, eh? ours turned out to be a GREAT deal)
3:00pm.. across the Missouri River and into Iowa enroute to Michigan on I-80
Midnight.. check into hotel room in Grand Rapids, crash on bed
8:30am.. meet owners at local retail store parking lot, unit looks great! Hook up... and we're out of there.
Back home in time for dinner.
I'll add... I've had good luck finding on craigslist via searching google using: +scamp +trailer +craigslist
Good luck on your search!