I recently moved in Japan and the game shop close to my house has just about everything PCE. And lots of it. The prices are a bit steep, but they have just about anything you're looking for. Here are some of the prices that I remember:
Duo RX (complete, in box) - $200
Supergrafx (complete, in box) - $175
Duo R (complete, in box) - $140
They also have some incomplete systems that sell for cheaper. That have RAU units, all 3 varieties of PCEs (PCE, Coregrafx, CoreGrafx 2), and accessories (contollers, AV cables, AC adapters). They also have a variety of games, but they tend to be a bit pricey as well. All items are in very good shape. I can pick any of these items up for those who want them, or if you have something you want me to look for, feel free to ask. The shipping charge will depend on the item, but I'd guess at around $70 or so to ship a system by EMS, or a bit less for air mail.
Please send e-mails to: valmain203@SPAMISBADhotmail.com (remove the SPAMISBAD bit, of course)