one-string bass

i saw Violent Femmes last weekend. and brian ritchie pulled out a
one-string bass. It was a stick similar to a bamboo. no frets and
sounded close to an upright.

It looked like a 2 string bass to me.
I saw a thing like this at the local art fair. It wasn't a bass and the
guy called it a "strumstick". I'm sure you could do a bass version.

He's no longer with us. He died quite a few years ago. but he was
brilliant. IMO. He used a slide as well. He'd alter tunings pretty
often between the two strings.

You are correct .
A couple of issues ago Bass Player had an article on Brian. It is an
Atlansia bass.