As many pointed out, any sturdy metal tube will work. If you know a plumber, scraps of copper pipe and tubing can probably be had obtained for free. Old golf club shafts etc. Brass tubing at hobby shops and Ace type hardware stores is not too costly. Short pieces of copper pipe from the big box Home Centers.

One of my favorites it to browse thrift stores for usable items. Got a coffee grinder for mixing dubbing for $1.91. Heck you might even pick up a golf club for a couple bucks just to cut up the shaft?