This is the company I ordered the nuc boxes from: http://www.customcardboardboxes.com/index.html
The rates were a lot better than buying from one of the supply houses and other custom box companies. She is a small company that does small orders. I wanted 500, but she was unable to fill an order that large in one shot. I ended up ordering cases of 50 at a time, but she would have done smaller orders than that. I got them in 19.25 inches by 8 inches id. If I ordered them again I would drop the extra .25 inches in lenght so the frames fit in tighter. What I ordered were also double corrigated which I would also drop down to just regular single corrigation. The stock is available in kraft or white if you wanted a traditional look.
My other advice is to check with your local PO prior to taking orders that required shipping. I had to cancel a few late nucs that had to be shipped because my local PO would only send them parcal post and it would have taken them two weeks to get to where they were going.
Always question Conventional Wisdom.
I'm going to use all medium boxes and was happy to be able to order a medium nuc from maine_beekeeper.
I think there should be a good market for them as so many of us are approaching geezerhood.