Google Shopping, Amazon, and AliExpress do not seem to support even the most basic constraints

I agree with your frustrations around those sites, but more structured ecommerce sites seemingly exist: https://mcmaster.com. Perhaps more common/valued in B2B than B2C?

considered joining the team at Metaculus or Manifold Markets

@DPiepgrass furthering this recommendation with Kalshi/Polymarket/ForecastEx/PredictIt/etc. Real money prediction markets address your growth theory concerns

Easter (April 20th this year) is another unique opportunity:
Likely less defensiveness addressing annual egg decorating/tossing/hiding/etc. than confronting daily diets

@VilleSokk created a similar calculator:
https://foodimpacts.org
https://forum.effectivealtruism.org/posts/KLqAiKpMpBCLCH6x7/ranking-animal-foods-based-on-suffering-and-ghg-emissions
FarmKind's donation call-to-action is a great add; you all should link up :)

Offsetting has multiplier effects.. people constantly make significant sacrifices attempting to marginally improve their personal sustainability, so publicly offsetting decades worth of personal impact with a weeks' earnings seems worth the statement

NB: I'd consider them regardless, but offsetting's a solid nudge 

Offset objections narrowly focus on future behavior; most people are raised omnivore; I'm offsetting past consumption:

https://forum.effectivealtruism.org/posts/HJtfDKDdFFHhDiJXM/recommendations-for-charities-for-animal-suffering-offsets?commentId=iq3SrK9K2q8zwsuBL

acting president [...] unelected official

While Musk is influential, it wasn't clear you were talking about him until your reply

Checked the 8 links in the first section and they've all been archived on the publicly accessible Internet Archive for at least half a year. There's also browser tooling to access those archives quicker

One concrete suggestion:
https://forum.effectivealtruism.org/posts/oZff425xLnikfxeGD/pat-myron-s-shortform?commentId=s8Qoydhg3zZ3b3486