I wouldn't go with a sleeved two-piece section unless I had to. The tubing comes in 20-foot or 24-foot sections, so getting a 12-foot piece cut should be no problem. When I needed it, I just did a Google search for aluminum tubing in my town, then got on the phone. Second place I called had exactly what I needed.

You can go with a two-piece, sleeved pole if you have to, of course, but it will be heavier and more complicated. Or, as others have said, pick up an old F2 windsurfer mast at a garage sale or on Craigslist.

Maybe my reading comprehension is not good - what are you putting this spin onto?