Why not grab one of the smaller XENYX mixers? If you're only using it for the EQ and don't need tons of channels, just buy a 502 or a 302USB. They probably use a similar EQ topology, and cost next to nada.

http://lmgtfy.com/?q=how+to+build+an+equalizer

The first link is relevant.

I have a DJ mixer already, 2 and 3 band EQs don't get the sound I want...
I SPECIFICALLY want the above mentioned frequencies of control...
Behringer doesn't offer 4band EQ in their smaller mixers, nor do any others that i've seen.

why not http://www.ikmultimedia.com/irigmix/features/

I had an insane idea and wonder if anyone out there is tech savvy enough to help me with this.

I want a breakout EQ box of some sort for my gameboy, specifically a 4band EQ similar (if not exactly the same) as the one found on my
Behringer Xenyx2222FX mixers stereo channels.

The frequencies are (low)80Hz (low mid)500Hz (high mid)3kHz and (high)12kHz

I've tried in vain to find the actual parts from the manufacturer. I'm this close to just ripping it right out of my spare mixer.

The circuit would require it's own power, be it wired into the GB or a separate battery.

I REALLY like the sound I get from this particular mixer/frequencies but the thing is way to big to take to gigs.

Any thoughts? I need all the help I can get. I've tried EQ pedals. None give me the sound I want. I want this sound.