Sources for M12 Lenses in 2018?

[obrienimages]

With regard to changing out GoPro lenses for aftermarket varieties of different focal lengths (3.37, 3.97 etc) has anyone found a cheap supplier that offers good quality? I've seen some posts saying the lenses purchased directly from Chinese manufacturers are good quality but haven't seen may links.
Thanks

 

[Dave Tolsky]

I’ve bought a few that way on eBay. Make sure the glass is rated for 4K if you shoot that.