I can't attest to a jap replacement, but you can get a direct shift lever from a 2002 Daytona. It replaces all the messy linkage with an L shaped arm that attaches directly to the tranny shaft. MUCH more direct shifting.
You can also get replacement parts (shift arm, linkage rod, boots) directly from Triumph. Got mine from Team triumph.
Your other option is to buy my linkage!! I have a complete shifter assembly for 99-02 RS and ST's.
chefjpd@netzero.com