Actually, there's no classical Fender tonestack, but a James one built in a perverse way, so that it's flat when turned all the way down. This particular pedal is also not very power-amp-friendly since it hasn’t got any buffer at the output. Seems like it won’t sell soon
Back then, I also built a Particle Accelerator one, which sold very quickly as it’s a very nice one with a classical Fender tonestack. The bloke who bought the latter was as happy as Larry.
So, back to topic, there’s Underground Accelerator by Sushi Box FX, which is basically the same as Particle Accelerator, but with one or two features more.