Nagaimo from non Asian stores?

[MoGa]

I live in London but find that nagaimo (Dioscorea Opposita) from Japanese food stores is rather expensive, especially for the quantities we eat (or would like to eat) at home.

When looking through the African and Caribbean stalls at Dalston Market recently, I noticed that amongst the many tubers there was one that looked exactly the same as nagaimo.

According to wikipedia, nagaimo is pretty much the only yam that can be eaten raw, the others have toxins and require specific types of preparation. As you can imagine, this isn't something I'd like to get wrong.

Unfortunately, I didn't ask the name of the tuber I saw that looked just like nagaimo, but I was hoping that someone with familiarity with African and Caribbean ingredients could tell me if there are any similar tubers that can be mistaken for Dioscorea Opposita, especially if these tubers can't be eaten raw.

- I'm also interested in sourcing yamatoimo/yamaimo and tororo (tororo pic: http://storage.kanshin.com/free/img_26/263015/k982549537.jpg ) - but these tubers also seem to be called Dioscorea Opposita even though they all seem slightly different to me.

Any help in making okonomiyaki more economical would be much appreciated.

Edited March 20, 2008 by MoGa (log)