Has anyone seen any Black Tuna around?

Good choice! Some of my favourite flower was Black Tuna in a can from THC Direct back in the day. Haven't seen it back there though.

Looks like National Compassion has it: http://nationalcompassion.ca/product/black-tuna/. I have not tried them.

I come across Organic Black Tuna every now and then,

It's a super potent high QUAD strain IMO, super gassy and pungent skunk smell..

One of my personal favourites as well.. will definitely give you a shout if it comes in stock

Thanks, best I can find right now is Tuna Kush