Those AirPax breakers show up on Ebay once in a while. I think they are model #239, back mount.
You could also try this guy:
Custom Marine Services
1548-B Francis Marion Road
Florence, South Carolina - 29506 USA
Hours Of Operation 9 Am To 4:30 Pm - Monday Through Friday
Closed Saturday, Sunday & Holidays
Tel --> 800.992.7922 - 843.673.2820 <-- Tel
Fax > 800-992-7923 < Fax > 843-673-2829 < Fax
Sams referred me to him for a rotary switch. His prices are not great, but he has alot of old stock. BE CAREFUL, though. My experience was that he does not like to take returns and he will try to blame you if you get the wrong part. Use a Credit Card if possible just in case you need to dispute it later.