I would add to Rod's post - the first place I would go to would be your favorite local OEM planter dealer.  Most of the planter dealers in the corn belt and some elsewhere have sold and can sell Dawn products.  Will they have any attachments in stock??? No, probably not. Life is not easy at the dealer level.

It seems like no dealer is willing to stock any complete planter attachments and maybe understandably so since customer preferences can change pretty quickly.  

As far as parts go, most of our Dawn wear items (bearings, seals etc) are common items at JD dealers. We can give you the cross over JD part numbers if the dealer doesn't have them already. Some of our better dealers are starting to stock a few common kits.

Jim at Dawn