Look for carbon fiber tubing. I got some from Tower a while back for just this purpose. I had made some pushrods of the 4-40 style a while back and I picked up some square outside round inside CF tubing from the LHS. The ID was just right to use the solder on threaded 2-56 adaptors. I rough sanded to OD of the brass and epoxied it into the tubing. The problem with this was that the brass in 2-56 size is very soft. I nixed that setup. I then found that a 4-40 thread would not quite fit the ID of this. I took a 4-40 tap and threaded the ID about 1/2" deep on both ends. I used a 4-40 short threaded rod, about 1" of full threads, and a dab of epoxy and threade the short rods in each end. I tried the same trick with the round CF I got from Tower, and threaded witha 2-56 tap and it would not take the threading, it split the CF lengthwise before the threads were in far enough. What I ended up doing is used a piece of 2-56 treaded on one end rod. I cut the threaded end off leaving about 3/4" of smooth rod which I kissed with my bench grinder to give the epoxy something to bond to. I then epoxied this into the small tubing. It has made a very good set of pushrods. Very stiff and very light.

Don