I recently came into possession of a Besson new standard 3-valve compensating baritone (for free???), and though I don't really have much of a use for it at the moment, it's a really fun little instrument to play! Haven't really checked the pitch tendencies on it, but I assume it's probably in line with most Besson horns from that era. Serial puts it somewhere around 1967-70 I think, from the databases I've seen. Those might be worth looking out for as well.
I do think unless you're playing 2nd baritone in a brass band, a 3-valve horn will probably do what you need it to do while being less expensive.
Sean Kissane
Low Brass Specialist, Paige's Music
Principal Euphonium, Indianapolis Brass Choir
Principal Euphonium, Crossroads Brass Band