Well, it seems like the MK2 version of the Sony MDR 1R is a well kept secret.
Sony let it be known, that they IMPROVED on the Sony MDR 1R with the MK2 Version..
Just a few, the MK2 version has better bass, and what was important to me in the BT verison, was that the MK2 included the aptx coding. There are other areas that the MK2 improved on too. However, it seems like Sony is/was being stingy on offering the MK2..I am in the USA, Bestbuy and all the vendors in the USA don't carry the MK2..In fact it is "gray market" to me. .However, the improvement was so much over the earlier verison, that I went and ordered one from an overseas vendor. I did my research on the vendor, and it was all good. I researched on what would happen if I needed warranty work on the MK2 version, and was given a full explanation on how that would be handled. Along with that info and a super price, I ordered the Sony MDR 1RBTMK2... Needless to say , the MK2 verison headphones have been perfect for me in everyway.
I said all that to say, unless you are in Japan, you will have to order them from an overseas vendor..There are some on Amazon selling them, and I went to AccessoryJack which I am well satisified, with their service and delivery time, which was all of about 9 to 10 days..