My Oppo Pm-3 pads were falling apart, but I couldn't find a replacement. ATH-MSR7 pads fit nicely, but you'll need to tear the original pads apart & keep the plastic base. Carefully
Oppo PM3 vs. Audeze Sine: battle of the portable planar magnetic headphones - The Verge
Earsoft Replacement Ear Pads Cushions for Oppo PM 3 Headphones Earphones Earmuff Case Sleeve Accessories|Earphone Accessories| - AliExpress
How to remove or replace Oppo PM3 Earpads *Video* – Everyday Listening
Oppo PM-3 : The Portable Planar - Impressions | Page 386 | Headphone Reviews and Discussion - Head-Fi.org