So the National Bonsai and Penjing Museum at the National Arboretum got back to me with an exciting opportunity. They are willing to give me access to their private collection of bonsai pottery (especially the American pottery) in exchange for some volunteering work. The volunteering will entail working with the pottery specialist to catalog and research the various pots they have in their collection. While helping out I'll have access to the pots and a lot of historical documentation on the pottery and trees. I'm meeting with them next Tuesday to solidify the details, but it sounds really cool. Thanks
@rockm for mentioning the museum's collection of pottery - it's what spurred me to contact them in the first place.