<<Disclaimer: Verify this information before applying it to your situation.>>
I would think you should be able to find English Muffin Rings through
Williams Sonoma (check online), or perhaps the King Arthur flour company.
Both of these companies have great catalogs.
Let me know if you need contact info
Bob at Ultimate Baking
Great Gluten Free Biscotti,
GF All Purpose Flour Mix and GF Heavenly Chocolate Cake Mix
http://www.ultimatebiscotti.com