Where can I buy chicken hearts?

Yeah, yeah, I know. Not another guy asking where he can source chicken hearts in the city. Check all the other posts, fella!

I've been prompted to resume my search for a butcher/store that sells fresh chicken hearts after eating some incredible duck heart skewers at Kushi-ya last week. My partner is Brazilian, and barbecued chicken hearts are something of a specialty there. I love them - really moreish and so easy to cook at home. IF, that is, you can find the little devils.

So yes. Anyone know of anywhere selling them fresh? In previous cities I've lived in they've turned up in world supermarket butchers (as well as the occasional Brazilian specialist store, but our local one doesn't have them!)

Help a guy source some tiny, tiny hearts that he will devour with the enthusiasm and ferocity others reserve for popcorn.