Custom ESCs?

[BrianG]

Maybe you can find an older style Mamba ESC, maybe contact Castle or Mike direct and see if they have any of the old ones still laying around?

Or maybe a Quark 22/33A would work?

Another option: This will void the warranty, but how about removing the sidewinder guts from the case, removing the heatsink (or using a much smaller one - even just a slab as a heat spreader), and resoldering the size wires you need? You could then wrap the whole thing in heatshrink and cut out a little window for the heatsink area. Even with the HS removed, heat shouldn't be an issue due to the really low currents involved.