Does anyone in the US sell R-core transformers to the hobbyist?

Hello fellow DIY Audio enthusiasts,

I have emailed a number of transformer manufacturers in the US about purchasing R-core transformers, and so far I have been unsuccessful finding a supplier for single quantity R core power transformers. I would prefer to stay with a North American supplier. Is there anyone in the US or Canada selling R core transformers to the hobbyist? Thank you.