A drawbar should be the easiest accessory you could make. The one that came with my SB9 was not an original SB but was made with a simple tube and a handwheel. The inside of the tube was threaded to fit the collets and a handwheel was bored out to fit the OD and held in place with a set screw. I don't have the dimensions here at home but will post them later if your lathe is also a 9". If you have another size lathe and a standare tube will not work, a nose piece could be machined from solid bar to fit a slightly smaller tube on one end and the collets on the other.
I added a thrust style ball bearing for easier operation. I highly recomend this feature but a couple of greased washers will also work.
As for obtaining an original SB, just set up a search on E-bay and sit back. It will show up sooner or later.
Make it fit.
You can't win and there is a penalty for trying!