I ended up preordering the controllers from Amazon UK. It says it doesn't ship to the US but you can order just fine. It comes out to be about $33 for each controller.
https://www.amazon.co.uk/NEOGEO-Mini-Console-International-Version/dp/B07DWHQG4W/
Oops. Auto correct strikes again. I'll leave it be since it's a funny typo.
The Buy 1 Get 1 50% doesn't stack well with GCU. There's only an extra 40 cents discount on the 50% off game.
Split it into 2 tiers and have each be alphabetical. BB/Target/Walmart should be in the top tier. Amazon just copies deals and doesn't really put out an ad while GS is pretty lackluster besides the used stuff.
People on Reddit are saying you need to use a VPN from a UK/EU location. Only after doing so will the "Invalid taxcode reference key 5 for subsidiary 4." error go away.