I'm surprised you haven't picked up a bodhran yet, Les - much less a cursed shakey egg or two. But all you really need is a bass drum with pedal to pound away one whilst playing your tenor banjo. This has the advantage of being a good place to display the band insignia so people know who they're listening to. If I lived a bit nearer I'd put together a vintage trap and do the job myself, like a down-at-heel Sonny Greer, whose gleaming percussion set was gifted by the appreciative gangsters who ran the Cotton Club.