If the Champ web site does not have replacement motors - IMHO, you are in the market for a new winch.
Suggestion - if you are going to purchase a new winch, choose a brand that does have replacement parts, including motors. Warn, Ramsey, Koenig.
Is it possible to just buy magnets for a electric motor?
AAHHH--- A wench out in the weather is not good. I always had a full cover on mine. Even with that I would totally unspool the cable and let it soak overnight in a bucket of hydraulic fluid & wipe down the entire unit with WD-40 or similar product every 3-4 months.
Are you sure the motor or magnets are bad. Have you tried the winch. I had one (not a champion) from HF that would hang up every once in a while. Never had it apart and always had it covered. Using the remote hitting the in / out button only resulted in the relay clicking but no winch movement. Relay was fine. To get it going I'd tap on the motor with a hammer. I think the brushes would get stuck on the one I had.
As mentioned brushes do stick, emery paper adjusts that.
Rapping with a hammer can detach the magnets that are generally glued in place and rust sometimes simply gets jammed between the magnet and rotor.
I have rescued a couple as well as a few DC motors that suffered those symptoms.
Unless shorted out (your nose will tell U) you should be able to salvage.
AAHHH--- A wench out in the weather is not good.
There are times I'd like to leave my wench out overnight in the weather too!
Fred