If you send an email to most baby product companies asking for samples and such they usually send them in the mail.
amazon: make a registry and buy something off of it i think is how you get a box.
target: go to customer service for the baby sample bag but sometimes they don't have it.
walmart/target has baby boxes for 5$ and it comes with a bunch of samples and i think free shipping.
go to enfamil, gerber and similac websites too.
if you have a motherhood maternity it's only like 2$ to sign up and you get a bag with samples and hella coupons
Target has a baby swag bag for making a registry but you have to get it from customer service in the store. Buy Buy Baby also does but you have to make a registry in store 😦
Noobie Box, Baby List, Amazon and Walmart have baby boxes but you have to pay shipping.