That actually looks a lot like the bass in the '76 Houston photo posted above (although not exactly)! And what a great pic--it's a new one to me!
NMB, do you think it may be possible this is from his days with The Poor? His clothes look very similar to what he wore in that "Ironsides" clip and the guy on the left looks a lot like Allen Kemp (granted, it's only a partial shot). If you know for sure it's during his Poco tenure, I will take your word for it.