Yes, they are 3D printing resin aftermarket.
No specific brand, I found them on a small shop on TaoBao (China). The guy is doing a lot of loadout stuff for aircraft all over the world (french, US, chinese, bomb, missiles, pods, pylon rails,...) and some figure as well at the main scale (1/48, 1/72, 1/144 mainly), so each time I go there, I order a lot from him

First time I went in China, and got access to TaoBao, I was really amazed by local aftermarket options. Some are available on AliExpress (not him, but you have FabScale and SSModels which also have great options of resin for aircraft, and Galaxy Model for resin and decals options, I some of their references), but most of them are just selling inside mainland China.
Maybe available to local TaoBao as well (like HKG or some others South-East Asia countries where the app is available), but I didn't try to check there as I only have access to the China mainland app.