It's "The Waterbed Polka" a.k.a. "The Waterbed Was Filled With Glue The Night That I Got Stuck With You Polka" by Larry Rand. As far as I know he never recorded it, but WFMT played it from a tape they made in 1972. I don't remember all the words but here are some:

I thought you was a hippie 'cuz you dressed that way.
I shoulda known them shopping bags sure gave you away.
But your Peter Max babushka misled me, dear, it's true.
The waterbed was filled with glue the night that I got stuck with you
polka.

I'm not in touch with Larry (if you're a Midnight Special fan, then you may have heard of my group, Molly & the Tinker) but a decent Google search might help, or maybe another Chicago folksinger knows.