Getting a vintage 2 stroke is a very good idea, modern dirt bikes/enduros of any size are huge. The only size my wife finds even remotely comfortable is an 80!!!! Granted she is borderline oompa loompa......
If you end up going vintage, which I almost did, check out www.collectorcarsandbikes.com. They usually have a pretty good stock of vintage 2 stroke enduros. Another thing to point out, I know most people don't like 2 strokes due to the pre mix gasoline. A lot of the older 2 stroke enduros were oil injected, which eliminates the pre mixing of the fuel.
Also older 2 strokes were not as "peppy" on the power band as newer ones. Most made power all on the low end like a 4 stroke, so you don't have to worry about a horrible neck snaping surge. Yamaha 360s were scary fast, my dad rode those for a long time and they will haul some ass. Bultacos, Honda Elsinores, Suzuki TS's and Kawasaki F-series are all great bikes. The Yamaha DT250 I see fairly frequently and price is usually hovering right around a grand.
ETA: If you need to ask anyone or just looking for information check out www.thumpertalk.com. Kinda like ARFCOM for 4 strokes.