The only smaller sized disposal that is worth buying is the Insinkerator Evolution Compact. If you don't have room for it, you might as well forgo the disposal. Most deeper sinks these days will require that the old waste arm to the drain system be lowered in the wall. That's a common issue that should be addressed by your plumber.

I just bought the Compact on ebay.

I would like to put a drawer under my sink. That is why I wanted the smallest. It may or may not work.

Thanks, Peke