Not sold at retail, but you can browse Freewell
Some links here are affiliate links. If you buy through one, Creator Gear earns a commission, at no extra cost to you.
Creators cited with this
Pierre T. LambertYouTube, 746K followers“So, on this channel probably 95% of all the videos outdoors you've seen have been shot with that ND8.”
Watch the video at 9:51
NigelBarrosYouTube, 163K followers“For the running stuff with my buddy Westy, I did use an ND8 filter, and that was just for the slow shutter stuff, but everything else was just shot bare lens with this little compact flash.”
Watch the video at 4:59
Chris HauYouTube, 616K followers“I actually have a filter set here from Freewell that is available that you can get ND8, ND16, and ND32 should you want to get that natural motion blur in your shots.”
Watch the video at 11:01
Creators who use this also use

Freewell Osmo Pocket 3 Filters
also used by 1 of them

Freewell Pocket 3 Filters
also used by 1 of them

Freewell Travel Tripod
also used by 1 of them

Freewell Tripod
also used by 1 of them

Freewell Variable ND system (Brandon Li collaboration)
also used by 1 of them
Freewell VND & CPL
also used by 1 of them