you have different options. The SL-5500G (German) isn't sold anymore, so you have to buy it used in ebay ... !
I have sold my old 5500 on ebay half year ago. There should be some offers over the time.
The SL-6000 was sold by trisoft (www.trisoft.de) but isn't anymore. Trisoft has only newer models. I bought my SL-6000L in USA in ebay.com. Very nice contact and with paypal np with payment.
The best option and cheapest, i think, is to buy via pricejapan.com. Look here in the forum for experiences.
Or you try http://www.linuxontour.de/
and make a wtb (wantToBuy)thread.
If you have more questions you can PM me in german!