Just wanted to compile the episodes that aren’t listed for sale or rent:
Anything bolded is known to not be available to Shout Factory in any form. Source: https://forrestcrow.proboards.com/thread/6297/likelihood-shout-factory-release-list
Anything Italicized is available on DVD in a collection on the Shout Factory website
Season 2: 201: Rocketship X-M, 212: Godzilla vs Megalon, 213: Godzilla vs the Sea Monster
Season 3: 305: Stranded in Space, 309: Amazing Colossal Man, 311: It Conquered the World, 317: Viking Women and the Sea Serpent
Season 4: 401: Space Travelers, 416: Fire Maidens from Outer Space, 418: Attack of the the Eye Creatures
Season 5: 522: Teen-Age Crime Wave, 524: 12 to the Moon
Season 6: 601: Girls Town, 605: Colossus and the Headhunters, 614: San Francisco International, 615: Kitten with a Whip
Season 7: 704: Incredible Melting Man
Season 8 (hoo boy): 801: Revenge of the Creature, 802: The Leech Woman, 803: The Mole People, 804: The Deadly Mantis, 805: The Thing that Couldn’t Die, 807: Terror from the Year 5000, 809: I was a Teenage Werewolf, 814: Riding with Death, 815: Agent for H.A.R.M.
Season 9: 901: The Projected Man, 905: The Deadly Bees, 906: The Space Children, 910: The Final Sacrifice
Season 10: 1001: Soultaker, 1010: It Lives By Night (Also on Amazon streaming), 1012: Squirm, 1013: Danger: Diabolik
Seasons 1, 11 and 12 are available in full