We did a seal replacement on a showa rear cushion ('19 FX) using a MOOSE RACING seal kit #1314-0047.
The MOOSE RACING seal is 4mm thicker than the stock seal which means the shock is 4mm shorter.
This measures as 12mm (1/2") shorter at the rear axle, hence the FX lowering kit.
Granted, the FX needs more suspension not less. The difference is barely noticable and this may be helpful for some people. I like the way it rides.
The options for a failed seal are:
Zero MC's FOX SHOCK for FX-ZM10-05738 / $700 usd
Zeromotorcycle part #22-08055 FX SHOCK 40mm / $450 usd
Zeromotorcycle FX SHOCK 40mm seal kit / NOT AVAILABLE
MOOSE RACING seal kit #1314-0047 / $50 usd
Plus labor of course, with a $400 reference point.
I have not tried the TEKNIK seal, a KAYABA shock seal head assembly 40mm od x14mm id x 21.5mm tall for $66 usd
The stock seal is 40x14x20
The Moose seal is 40x14x24
WARNING: The shock contains high pressure nitrogen!
Nearly all shops will replace the seal and nitrogen, especially if you know which seal to use. A shop near me did the job on one for $200.
Ride On, Red Clay