Looks like Allbirds sent some of their clearance stock to Sierra and the prices are quite a bit lower than Allbirds’ own site. Free shipping on $89+; free pickup at a local store may also be available.
Sizing availability varies a lot by style. I believe that there is not much of a difference between their men’s and women’s casual styles – for example, my wife finds that a men’s 8 lounger fits her the same as a women’s 9.
Note that Sierra’s site does not let you search using the keyword Allbirds (presumably due to a minimum advertised price agreement), so I suggest going to the shoe category and sorting by brand since they will be towards the top.
Women’s:
• Tree Lounger (Lux Purple/Blizzard) $34.99
• Tree Skipper (Navy Night/White) $34.99
• Wool Lounger (Diablo/White) $34.99
• Tree Piper (Wasatch/White) $39.99
• Tree Piper (Blue Ridge/White) $39.99
• Wool Piper (Diablo/White) $39.99
• Wool Piper Mid (Heathered Black/White) $39.99
• Tree Dasher 1 (Geyser/Light Blue $49.99, more sizes at this link for some reason
• Tree Dasher 1 (Thunder/White) $49.99
• Tree Dasher 1 (Obsidian/Black) $49.99
• Trail Runner SWT (Diablo/Orange) $49.99
Men’s:
• Wool Lounger (SF Grey/Grey) $39.99
• Wool Runner (Frost/White) $39.99
• Wool Runner (Diablo/White) $39.99
• Wool Runner Fluffs (Natural Black/Black) $39.99
• Tree Dasher 1 (Geyser/Light Blue $49.99
• Tree Dasher 1 (Puukeko/White) $49.99
• Tree Dasher 1 (Obsidian/Black) $49.99
• Tree Dasher 1 (Thunder/White) $49.99
• Trail Runner SWT (Diablo/Orange) $49.99
Socks:
• Trino Spinters Cushioned Low (Onyx) $4.99
• Trino Spinters Low (Flame Geyser, or Lightyear) $4.99