The 2" heavy wall square tubing that's used to plug into trailer hitch receivers works well, and most places that build and/or install hitches just might have a piece of that stuff around for custom fabrications. A welding shop should be able to cut you a couple of short sections, also.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!