i've been lookin into it and i think i can make one for around 20 or so with line out, and usb for about 20-25 bucks or so. functionally, it would act like
this guy, but not have a dc-in port, and would charge through usb. it looks sorta like the this.
_____
|____| to DJ
|
iiiiiiiiiii|
|
iiiiiiiiiii|
\
iiiiiiiii/
||_||
// \\
|| ||
|| [] line out
||
ii\'============[] USB
i've been wanting to do one for a while now, but have had no reason as i have a dock.
let me know if you are interested.