I'm not really versed on things on this front, I'm just wondering, did you mean to buy SN? Sodium Nitrite. I'm asking because I've seen mention of other salts that are not ideal. Is sodium azide actually what you want? I know sodium nitirite is the recommended ctb method by many here.
As for the site, it's pretty comprehensive from a scientific standpoint. It's clearly put together by someone with knowledge which is a good sign I guess. They appear legitimate. Will they sell to private residence? Who knows. The fact you don't need to log in to make purchase suggests yes but also raises a bit of a red flag. I think it's probably a wait and see situation for you though I'm afraid. May have been better to query it here before making the purchase. Was it expensive? I'm sure they'll notify you if the order doesn't go through.