Window "brakes" - What are these things?
In many cases, repair of really old wood windows can be as or more expensive than replacement due to a variety of factors, one of which you have found--unavailability of off-the-shelf replacement parts. And after you're done, you still have leaky, single-glazed windows! I would only consider repairing these windows if they have architectural or historical value to the house. If they don't, you may be better served by replacing them with modern, well-sealed, energy-efficient windows, which come in wood if you like that look. You can even get windows that are wood on the inside and aluminum or fiberglass on the outside, which really improves their durability and reduces maintenance.