Cody,
I don't have a lot of advice to where to find them, since I have kept and recycled packages that have been used to send bows to me (if they were well packaged).
With the exception of one bow that had a custom built wooden box (it was the best bow packing job I've ever seen!), they have been in thick cardboard boxes or tubes (such as the center of carpet rolls or long thick cardboard boxes that contained construction items such as flooring).
They were larger than the actual bow (say a 6" tube or or 5"x7" box to hold a 2" diameter longbow, with bubble wrap or newspapers taped around the ends and around the grip area, holding the bow firmly in the center of the box/tube. I think this is so there was a good "crush" area that could be damaged without ever actually hitting the bow. Often the other empty space would be filled with newspaper but not always.
I do think the thing (IMHO) that made the BIGGEST difference was the majority of what I have received and everything I have shipped came or was shipped USPS Priority. The longer the package is in the hands of the shipper, the more likely it is to be damaged (in my experience with shipping and/or receiving 9 bows, and a few years of shipping/receiving experience in my career).
Anyway, there you go for what it is worth!
Ron