I was able to source all the parts on Amazon domestically except the relay, which either has to come from a parts specialty place, or from a Chinese seller on Amazon marketplace or eBay.

Main fuse: https://smile.amazon.com/gp/product/B09JPFMMY1/

Primary door switch: https://smile.amazon.com/gp/product/B002CRSOR0/ (use only the bottom of the two side terminals and cover the other with electrical tape; this is the one recommended by u/HeadOfMax)

Secondary interlock switches: https://smile.amazon.com/gp/product/B09NCSFWRR/

Relay:

https://smile.amazon.com/Relay-JQC-25F-018-H-20A250VAC-Microwave-Dedicated/dp/B0B9NYFJNW/

https://www.ebay.com/itm/364034554131
https://www.ebay.com/itm/122376501546