Source For Styrofoam Packing Inserts

There are a number of brands of expanding foam bags that will… well, create foam and conform around whatever you are packing. You would want large ones. Amazon has a number of them. I would search google to find the right size.

Probably a long shot but you could try contacting PSB dealers or the national distributor. Normally the packing is necessary until delivery, then most owners want to keep them.

Thank you everyone for your suggestions.

@facten I forgot all about Uline.

@ghdprentice I know exactly what expanding bags you are talking about too.

@tcotruvo Oddly enough, PSB could only provide the new boxes. They did not have any foam inserts to sell me. That still has me me scratching my head.

Another "custom-made" option might be the styrofoam "popcorn" packing used to protect fragile items during shipment.  It is extremely flexible as far as fitting into every nook and cranny, and is surprisingly strong once packed in tightly.  I have a bunch of it I'd love to recycle, but unfortunately, I'm up in Canada.

I’ve shipped heavy speakers around the world. No issues, thank goodness. 
I buy 2” styrofoam foam from H Depot and cut to fit. 
 Ain’t Nothing Like The Real Thing- but it works in many situations. 
Good luck.