I’ve finally found some panniers that fit the TC Max, cheap too!
https://www.sportsbikeshop.co.uk/motorc…/content_prod/279271
The bottom straps can be fitted under the frame and around the grab handle which means that the seat can still lift off cleanly for access to the kill switch.
You can fit the velcro underneath the seat release mechanism, then by separating the Velcro by sliding a piece of thin card between the two halves you can place the other half of the Velcro and press it shut. Once that’s done it doesn’t affect the seat closure at all.