It's a metal rod about 18" long and (I think) about 7/16" diameter, with slightly chamfered ends. This Forum's moderator Reid Trummel had some repros made a few years ago. I think you could make a decent one with some rod and a grinder.
The jack number sounds right, but I'm not positive. There are two versions of the jack, the later/best one has some additional webbing to reinforce the hole where the handle goes. They come up on eBay once in a while, but usually go for $300-400.