Thanks for the replies. I pulled it out and found the rod is held into the cylinder with an easily removed c-clip, but certainly can't find just the rod anywhere. If I'd had a flashlight handy, I would been able to see that the rod assembly could actually be switched out with the cylinder still in place...oh well.
I'm going to go check the offering at the auto parts place tomorrow, hopefully it'll have the steel rod. Looking at mine, it looks like the metal rod is actually made of two separate parts, fit together in ball-and-socket fashion, then held together by a plastic sleeve formed around the two pieces. Kind of a screwy set up. I've priced the cylinders from $25-40 at scrap yards, $55 new at Pepboys.