I have an auction on eBay for a phat silver Nintendo DS with a patched firmware which allows you to launch homebrew (and NDS games) from the GBA slot (with a supercard type storage device, not included). The patch also skips the health warning on boot up. System is adult owned and comes with a sealed copy of Kirby - Canvis Curse and the AC Adapter.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=220218448548&ssPageName=STRK:MESE:IT&ih=012
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=220218448548&ssPageName=STRK:MESE:IT&ih=012