I'm about your age, just getting to know my SB 10L. After a long session with the old soldered water pipe that came with my lathe, I decided I could do better. Your spindle is identical to mine I believe, albeit longer.
I rounded up some 4130 DOM tubing, a thrust bearing, handwheel, etc and covered my bases by getting an indexable inside threading bar, along with a few taps. The taps work fine, if you don't mind breaking a sweat for an inch of fine thread!
I can't believe how nice it turned out. Them, I mean. I made a couple. I get a hard lockup with SB collets, and the new imports which have a different thread length. I spaced the wheel for good finger clearance and gave myself all the thread engagement I could. I cut a slight taper on my spacer so it centers itself as it comes up tight. And it does come up tight with that bearing! All it takes to release it is a quick one-handed push, and the wheel design lets me spin it with one finger.
I might be able to fix you up with plans, materials, semi-finished kit, or complete drawbar. I do feel your pain! If I had known a handwheel closer could work this good I would have saved a lot of time spent drooling over lever-style closers online!