My understanding about the R606 supply is that there were only a few left that were purchased over the last number of weeks. They have officially been discontinued but the orders have still not shipped. I have one on order through bitcoinmerch and one coming from 419mining as a replacement. At the time of purchase there was a 4-6 week wait period which has now come and gone. Still waiting.
If you're extremely lucky you might be able to find one in the wild that someone is wanting to sell on e-bay or amazon but chances are pretty slim one will pop up.
Send a PM to sidehack and see if they still have one in the shop. Ya never know.
Ya might be better served to pre-buy the next batch of the new Apollo BTC miner instead. Have a look at it. About the same cost but twice the mining power for a few more watts of juice.
Announcement thread here:
https://bitcointalk.org/index.php?topic=5314398except that's a preorder so pay now and wait a few months to get it. Hoping sidehack puts out a new btc one without a preorder and wait. I have 4 r606's running now and love em.