As said elsewhere, it's actually 'sodium nitrite' and searching for 'sodium nitrate' does not show the relevant suggestions. For anyone that might be curious to search it from this comment.
Searching for sodium nitrite and selecting a seller of >98% on Amazon (US) did give a suicide-instruction book as a suggestion when I searched initially (logged out, private tab), but after looking up the SDSs and coming back to this, I no longer get anything of the sort.
I doubt that legitimate chemical suppliers like Fisher/VWR/Sigma-Aldrich/etc would sell sodium nitrite to a buyer without an approved account (though VWR if I recall correctly won't sell chemicals at all to residential addresses, even sodium chloride, so it's not necessarily the best comparison).
[1]: https://www.alfa.com/en/msds/?language=EE&subformat=CLP1&sku...
[2]: https://www.fishersci.com/store/msds?partNumber=AAA186680B&p...