I'm trying to get my hands on a marked heron blade but they are impossible to find anybody know where to look? or maybe are looking to sell?

Unfortunately I can't help you :(

All the swords I have at home are real medieval replicas but have you tried etsy?

You could have one custom made.

http://www.omegaartworks.com

Look at custom katana makers. You can get cranes on those.

 

And, yes, I know it is supposed to be a heron - but cranes are a lot more common on Japanese swords, and what is the difference anyway...?