Don't give up on that collet closer tube. If it isn't kinked, odds are you can massage it back to round.
IF all else fails, you can either make a new tube or cut the end off and weld on a new piece.
I made the complete assembly for my 10K and it wasn't all that hard. The most difficult was learning to make the internal threads and getting them the right size. I used up a bunch of black iron pipe doing practice runs. My collection of used 6K collets had quite a lot of variance in the threads.
That hand closer is definitely worth saving or at least restoring/repairing.