I assume it uses a universal motor like most consumer market blenders do. (Some professional blenders use inverter drive motors, but I'm pretty sure trying to run one of those on half voltage will cause an error and not let it work at all.) Universal motors will also run on DC, so rectify AC to get 170V DC - you can easily find the bridge rectifier, NTC inrush limiter, and capacitors in a discarded PC power supply. Combine that with inductance no longer being a factor and it should get pretty close to the original 240V performance. Beware the original switch isn't designed for DC so use it to switch the AC going into the bridge rectifier.
There's also a trick of building an inverter to create another 120V waveform out of phase with the existing one, for a total of 240V, but that's a bit fancy for just one simple appliance. Might be worth considering if you have a lot of devices that need 240V.