Game Boy Color/Pocket/Light 3.3v USB Cable
So I went in search for these.... I couldn't find them off the shelf so I've had them made for me.
The cable drops the 5V USB voltage down to roughly 3.2v this is very close to the supply of 2 AA batteries (1.6v each = 3.2v)
The lead has a Male USB 2.0 plug one end and a 2.5mm straight DC barrel jack the other.
They are 1m/1000mm long or 39.5" to the imperial folks approx
This cable is the same for Game Boy Color, Game Boy Pocket and Game Boy Light consoles
Review for Game Boy Color/Pocket/Light 3.3v USB Cable
I wouldn't trust any other cable for USB power to your GBC. This works perfectly with my portable battery if my AAs run out of juice. I had another cable I bought from HHL and it concerned me with how it was functioning (half the time it worked, half the time it didn't) and I think it was sending the wrong voltage which could lead to potential hardware issues in the future.
REALLY happy with this! Highly recommended.