PM → FMアダプター
Adapter for Flat Mount Caliper on 140 mm Post Mount - A.S. Solutions
https://www.assolutions.ca/shop/adapters/flat-mount-brake-caliper-to-140-post-mount-frame-fork-with-140-rotor/

Flat Mount Caliper to Post Mount Frame Photos - A.S. Solutions
https://www.assolutions.ca/flat-mount-caliper-to-post-mount-frame-photos/

自作した人
Adapter for Flat mount caliper on post mount frame - Tech Q&A - Bike Hub
https://www.bikehub.co.za/topic/177590-adapter-for-flat-mount-caliper-on-post-mount-frame/

これまで何故大手が出さないのか分からなかったが、現物を見て漸く理解した