Stewart Wilkins (02-4577-2400) had one for $400 about 2 years ago, he might still have it. He can also do close ratio sets using 240Z parts, but it isn't cheap.
I recently swapped a stumpy box for a stanza 5 speed, H165 tailshaft, manual pedalbox, engine crossmember & probably the speedo cable. I have a couple of long L series boxes if you want, but you could just get a series 3 bluebird box with the CA bellhousing & (according to Stewart) a closer ratio gearset than the stumpy box, mainly in the gap between 2nd & 3rd.Give him a ring, he might even have a box with the CA front half & you could part exchange your one. Good luck.