Fire giant toes
 

Anyone know a merchant known for selling these? I already checked the druid ring in Firestorm, nothing there.

Check the merchant on AC island in OOT. If you can't find any, the is a named hill giant on Seafury island that drops them. If you are too low to kill him, maybe somebody killing Seafuries will do it for you. If not, I can help you out around 1am EST.