I have an Urban and found the same problem, no one makes one that is a direct fit. After much research, I ended up using a variator for an early (pre ‘93, I think) Honda Dio/Elite. Even then, I had to mod the bushing by trimming about .060” off the length. I bought a 15mm reamer to run though the ID (stock Urban shaft is 15mm, Dio is 14mm) and machine the bushing OD about .100” to fit the new variator bushing ID. This dimension needs to be hand fit to the bushing in the variator for longevity. Also, the OD of the variator had to be lightly cleaned up on my belt sander about .010” because it barely touched the kicker assembly when running with the various component play and clearances (yes, it was that close for this manufacturer).
The variator itself wasn't too expensive and has a different ramp system that gives it a different response than stock. I bought a cheapo digital scale at Harbor Freight to check the weight of the standard rollers @ 13g each totaling 78g’s! The new variator came with 9g and I bought some 6gs. I’ve played back and forth with it and depending on where you want the power to come on (basically raising or lower the stall speed of the clutch) I’ve pretty much settled for a combination of 3-9’s and 3-6’s for 45g. total weight 6X6g – 36g gives you a fun take-off blast but is short lived. Having a little more, even weight distribution yields smoother, overall performance.
There’s some controversy on using 3 weights or a combination of weights, I’ve tried them all. I run it dry and don’t use any grease like stock did. The weight mod take me less than 5 minutes when I’m tuning with my open observation cover and a 3/8” drive butterfly impact gun. No changes to the belt, still running the one that came with the bike.
You can view the installation and live action operation on a You Tube video.
Google search: Extreme Urban Express Clutch Operation
Or, search You Tube: Routabit - for all videos related to Honda Urban Express tuning mods