There are frequently spool guns on eBay, but most will require a control box, which is sometimes included. I have the Airco Miget 20-E on My Airco Dip Pak 200, it uses a control board that fits in the front pannel of the machine. I have also built a control that will drive these guns from off the shelf parts.
I don't have a Spolmatic 1C, but I think it might direct connect to Your machine because of the 4 pin plug.
Some of My friends have the older Spoolmatic guns, I think they are satisfied with them. One friend has a MK Prince, it is real nice. I think any of the industrial units will be OK, but having said that I do have an old Air Products unit that I think was made by CK Systematics, it is a bit twinky compaired to the Miget 20-E. This unit looks much like the Hobart SP 2000 and Lincoln Magnum Spool Gun. I never used it, It is pretty light and compact, it might work OK.
Another alternative for light use might be the inexpensive Miller & Lincoln guns [$190-250 new, on eBay], but I think You will have to figure out how to make them work with Your machine. They direct connect to the machines they are built to fit.