Armed with visual info, I went digging last night and found a number of buildings that could work as proxies.
For the church, there is the Terrain Shed kit linked up above, and for a pricier pre-painted option 4Ground has a Church set with picket fence and grave stones
Sarissa makes a very nice covered bridge, and one of their 2-story Dutch-Belgian townhouses could stand in for the Van Allen House. Their Post Windmill would be close with a stone sheeting added around the post framework.
Things From The Basement has quite a few proxies, Barn, Town House #1, Town House #2, and Watermill (I think there's a Watermill on the village pond, but you never quite see the wheel on the building in any screen shots).
The biggest piece missing is something for the big Van Tassel Manor.
A better proxy of the brick Van Allen House in the front left corner of the illustrations above would be good.
Any sort of proxy out there for the Sleepy Hollow Inn, the thatched one in the front?