Ok that worked a treat, the new dust boot is now in place. For future reference the Nissan part number is 32862 (BOOT RUBBER C/L). About $10 + postage off eBay.
I also got the nylon bush from a local Nissan dealership, the part number is 32861-H7301 (BUSH CONTROL LE) - this is for R34, R33 is different. Just Jap also sell these: http://justjap.com/index.php/genuine-nissan-gear-shifter-lower-bush-nissan-s13-silvia-a31-cefiro-r31-r32-gts-and-gts-t-r33-gts-and-r34-gt-t-and-gt-r.html
One more question: How do you install the circlip that holds the upper plastic ring (and the gear lever) in place? Mine seems pretty loose but there's probably a trick to make it work.