Below is the text of a message I just posted on a Rex6000.org message board about my search for a new Rex 6000. (I believe PCMall.com and MacMall.com are the same operation.)I recently bought a new Rex 6000 to replace a broken Rex 3000 and though I would share the information I collected about availability and prices.
Sadly, some of the U.S. outlets listed on the Rex6000.org site no longer appear to sell the Rex 6000. I found only three online retail vendors which claim to have the Rex 6000 in stock: MyPC21.com ($89.99), PCMall.com ($98.00), and eCost.com ($98.99). These packages all include the serial docking cradle. Prices are exclusive of shipping and any applicable tax. I have no experience with any of these vendors. The RCSeshop.com site is down for "maintenance," but you might try calling their Manhattan store at 212-949-6935 to see if they still stock the Rex 6000.
I ended up buying a new unit on eBay. There are two eBay sellers who have a supply of new, sealed Rex 6000s and post auctions on a regular basis. All include the serial docking cradle. The winning prices on new units during the period in which I was bidding ranged from $66.00 to $102.50. I paid $71.00 plus $15.00 shipping. You have to be patient in order to get the lowest price. If you don't want to wait, the eBay seller from whom I purchased (tessiedef) also makes the units available at a set "Buy-It-Now" price of $85.00 plus $12.50 shipping. I would post a direct link to the listing here, but I'm not sure that is allowed. I had no problems at all with this seller and received my Rex 6000 right away.
It seems that the best online prices on a new Rex 6000 including shipping are at MyPC21.com and on eBay. I assume that prices for used units on eBay should be lower than those for new units. I decided that having a sealed package was worth extra to me.
If you need a USB cradle, they are also available on eBay, but the lowest price I found online was at ComputerGeeks.com (only $4.25 plus shipping). Note that this does not include the USB cable which could run you $15.00 or so at Radio Shack. I happened to have a cable on hand, so I ordered a cradle from ComputerGeeks. They initially sent me a serial cradle by mistake but corrected the error quickly. If you do not have the right cable, you might be better off finding a USB cradle with cable included on eBay.