There are quite a few more companies out of business than that, especially ones with less than three or four discs that you may not be familiar with.
I'd like to have a complete list of companies no longer making PDGA-approved discs. Any volunteers here want to work on that project? Here's a complete list of companies by year:
1978
1 Wham-O/DTW and another Chinese company that bought Wham-O who was making actual Disc Golf Discs though they now only make the starter set.
1979
2 Destiny/Dynamic (original Dynamic)*
2 Discraft
1982
4 DGA
1983
5 Innova
1984
6 Lightning Almost dead Gotta Go Gotta throw owns them and molds, right company they had the bags made for Lightning.
1995
7 Millennium
1998
8 CHING*
8 Gateway
2001
10 Plastic Para. Not sure
2003
11 Aerobie
2005
12 Discwing* one of the fastest ever deaths to a company that actually made discs.
2006
13 Discmania
13 Latitude 64
13 Pacific Cycle Yes those really bad discs with Pluto driver, Saturn midrange, and Mercury putter. brother was given some from a friend and he threw them one time and had disc warping, often come with a Disc Basket by same company.
13 Quest AT, yep still making discs in a Champion/Z Like plastic with the 10 Meter Brick as floppy as a Aerobie Dogobie.
13 RPM/Aotearoa
13 Snap* I think so they are dead? Only disc I remeber they made was the Whittler.
2007
19 1080 These can be found but it takes work to find them.
19 Daredevil
2009
21 Hero Leports Not sure as it is a European only company
21 MVP
21 Vibram* even most of the 5 finger shoes are not being made anymore (Lawsuit).
21 Westside
2010
25 ABC
25 DKG
25 Prodiscus
2011
28 Crosslap*, they made discs? well the company is gone they do not make the cart anymore or have a way to contact company.
28 Ferris State, they make a disc I think?
28 Legacy
28 Rip
28 Skyiron
28 Skyquest
2012
34 Dynamic
34 EMSCO
34 Eurodisc Still does, even a putter that is too stiff for PDGA but not a Disc Golf Europe thing separate from PDGA.
2013
37 DMI
37 Kastaplast
37 Prodigy
37 Salient*second fastest death of a disc golf company after Discwing.
37 UB
37 Yikun
2014
43 Axiom
43 Deity
43 Essential
43 HOLE19
43 Obsidian
43 Paradigm
43 Reptilian
2015
50 AquaFlight I think they still do? I find the discs selling out as they are all water discs
50 Element* the owner has just put out a statement saying he has since 2017 bin making stamps only for other companies discs, they just ran out of original discs well most popular disc that fat putter.
50 Fly High* I though they never made it off the ground and only had the old approach Wizard mold at minimum quantity?
50 Las Aves
50 Ozone
50 TOBU
2916
56 Black Zombie
56 Disc King* Yes dead they had the 21.7 cm Diameter putter hat could be up to 180 grams.
56 Full Turn
56 Guru Disc
56 Plastic Add.
56 Viking
2017
62 Above GL
62 Arsenal
62 Best
62 Galaxy
62 MINT* Might be gone or they only make a single mold still.
62 Sportme
62 Streamline
2018
69 ACE
69 Albatross
69 FLYTEC
69 Fourth Circle
69 Infinite
69 Kestrel They make both a set in a Champion/Z like plastic and a Baseline.
69 Storm
2019
76 Disc Golf UK