correct me if I'm wrong, but the '06 pista has ISIS Truvativ touro cranks, right?
if that's the case you have a 68x108mm ISIS BB.

the only ISIS track crankset I know of is the FSA vigorelli (well, there's also an OEM FSA carbon model)

so you could get a replacement touro (which is really a triple with the ring mounted on the inside) for $60-ish.
or a FSA vigorelli for ~$175. (but i think it's fugly and the old versions were known to suck)
or you're looking at a new BB + crank combo. Sugino 75 is in your price range - do a search, i thnkg mud sweat and gears has the best price. Miche would be a bit cheaper if you're willing to deal with 135 BCD rings (try ital-tecno). Don't get the stronglight.