Possibly you have not found Rainier because it is not really suitable for growing in the UK. Brogdale (Kent) has it in their collection, but there are hundreds of other cherries suitable for growing here.

Here is a link that might be useful: National Fruit Collection.

Thank you. I had not been able to trace it at all.

I realize it's not ideal for the UK climate but I just love the fruit! I am growing a UK-originated white cherry but the fruit is not nearly as good. So I just wanted to try growing Rainier as well.

Thanks again - Blanka

http://www.delbard-direct.fr/tous-nos-produits/arbres-fruitiers/fruits-a-noyau/cerisier-rainier.html
I hope this helps. I too am interested in growing a rainier cherry tree in the uk even though it doesnt seem to be ideal or the plant. Im sure its possible to get one sent over from france to the uk.

I realise this is a really old post but did you manage to get hold of a rainier cherry tree as I am also looking for one. Any advice you can give is much appreciated.