Gameboy Advance SP - headphone/charger splitter?

[Jorpho]

Yes, there is one made by Madcatz. Here's a picture of it:

Can anyone at least figure out which Mad Catz kit might have included this thing? It's not the Starter Kit SP, nor does it appear that it was sold separately.

EDIT: Ahh, it's the Macro Kit! Unfortunately no one is selling one.