I recently started playing with a blues harp player, and I'm having some of the same problems. Maybe I should try using the metronome I've got and tend to ignore.Re the drum machines: I don't know if they still carry them, but Radio Shack used to have a fairly sophisticated drum machine — lots of rhythm patters — that wasn't very expensive. I don't remember exactly, but I think they ran about $59 or $69 bucks. Maybe if y ou can call Lonesome EJ out of the woods he could tell y ou more about what's available there.
Just a thought: I try to think of body rhythms — walking, skipping, running, etc. — and I find almost all songs will fall into one of them. Of course when you get into jazz and sambas and things like that, it might get a little more difficult.
cheers
david