Have you checked with people at the Tahoe Yacht club? They've been running a regatta for years in early June, might know of some boats in the area. I don't know them myself. there's no rowing on Donner, but years ago USOC ran some development camps up there.
Stanford operates a retreat on Fallen Leaf Lake for alums and faculty/staff, they have a small fleet of old Pocock trainers, not sure how helpful that is.
There! I've exhausted all of my Lake Tahoe area rowing knowledge in a couple sentences....