Brake levers?

Thought I'd take the opportunity to make a fool out of myself by asking what's probably going to turn out to be an obvious question. I've done shedloads of research, but am still not quite sure...

I have Nitto RB-18 bullhorns, which Hubjub say are a 26mm clamp. I'm currently running a TT-style lever at the end of the bar, which is a waste of time as that's not where my hands are when I'm wanting to brake.

If anyone uses the Nittos and has a BMX-style lever, or just happens to know what will work, could you let me know? It can be left hand or right hand - doesn't matter too much - but I'm just totally confused on what's going to work as hardly anyone lists the clamp size and the last thing I want to do is end up with a stack of very pretty looking levers that are too small to fit my bars.

Anyone? No-one?