I've been doing repair for a living since 1972, and have overhauled and repaired literally thousands of saxophones. In far less than 1/10th of 1% have any "factory" parts been necessary, and this has only been to replace components that have been lost or were too far gone to repair at a reasonable cost. It just doesn't come up very often. When it does, any competent technician should be able to fabricate just about any part necessary. If you don't have the ability to make a key, you should get out of the repair business. This is a good way to judge a technicians skill level: can they fabricate a part or are they merely a "parts changer"? That being said, most companies that manufacture horns (including my own) make parts available for current production models. Parts for older horns are quite another matter, of course. I believe Selmer USA has a policy of providing parts only for instruments produced in the last seven years, although I'll stand for correction on that if It is no longer the policy. Yamaha and Jupiter both provide extensive parts availability. Some companies provide parts catalogs, but they are the minority. Since many brands currently imported are not proprietary designs, but are "off the shelf", parts for a given instrument may be available from a wide variety of sources. You just have to know who actually builds what, and again, this is information that any competent technician should have readily available. When I order horns, we include a supply of likely needed parts along with the instrument order. I think most companies do this. Obvously I don't stock every part in every finish, but what I don't have is readily available from the factory, and any key can be plated in any required finish. Most companies don't inventory parts like body tubes and bells, since if you need to replace those expensive parts, the horn is most likely "totalled". In my almost 40 years in the business, the most common requests are for pivot screws, key guards, and high D keys. Rods are easily fabricated from raw stock. Many of the Asian made horns such as Mauriat and Cannonball use common components, and these are easily obtained if you know where to go, as anybody who is in the repair business should. I maintain a large supply of generic Asian parts, as do most larger shops.