Needing replacement crank mechanism

We purchased 77 casement windows from Beechworth. Unfortunately, 4 are not working. When we turn the crank, nothing happens - nothing moves and window doesn't open. It appears that the mechanism is stripped. We need to purchase at least 4 of these (2 left and 2 right). Beechwrth went out of business about 2 months after we purchased the windows, so they are no help at all. Hoping you're able to assist. The hardware appears to me manufactured by Truth.