Have you thought about looking at Clifton? Mostly bigger barns off the Battlefields, but Clifton and Nokesville aren't too far and have more smaller, private barns. I would check the board at Dover, Saddle Liquidators in Gainesville, and the Clifton tack shop. Or hopefully someone will PM you with an opportunity they know of...trail access will be the key.
"Our greatest glory is not in never falling, but in rising every time we fall." - Confucious