I just bought one from this website.
it's so cheap. on ebay it was around 70 dollars. and some of the mod website they sell it for around 45 dollars. ~
i think this is the cheapest place where you can get R4 for your ds system.
there is Chinese version(28 dollars shipped) and English version(30.69 shipped)
get it before it becomes OUT OF STOCK~ Hurry~
also you can get 1gb Micro SD card for $10.95 dollars shipped (DEAD)
So total you gonna spend $42 dollars if you need english version, $39 dollars if you get the chinese version one. and Ready to do some home brew games and everything~
Check this site out, where you can download All DS games for FREE~