Found: A.S.Solutions Flat Mount Adapters for Post Mount and IS frames and forks - Bikerumor
BUCKLOS MTB Hydraulic Disc Brakes, Mountain Bike Left Front 800mm Right Rear 1450mm Hydraulic Brake Set Aluminum Alloy Levers with Calipers PM/is Adapter Fit EBike /Fat Bike : Amazon.in: Car & Motorbike
Adaptateur pour montage d'étrier de freins à disque sur cadre de vélo VTT, accessoire avant et arrière, rotors 180 mm/203 mm, en alliage d'aluminium, IS/PM - AliExpress
Adapter for Flat Mount Caliper on IS Mount Frame - A.S. Solutions
Disc Brake Adaptors Unraveled
Hope Brake Mount Adapter – BRINK
140mm | 160mm Flat Mount Brake To Post Mount Caliper Conversion Adapte – Dcbikes