Tomato mill? I assume since you mention electric then you don't want a chinosis so that leaves the Kitchen Aid attachment many use if you have a Kitchenaid mixer, the Victorio, the Squeezo models, Norpro, and the Roma models. Many discussions here about the pros and cons of each.

All have the option of adding a motor to them for extra $$$ but there are pros and cons to motorizing them - bigger mess for example as well as more product waste. Personally I have the motorized attachment for my Victorio but quit using it and I can't recommend motorizing any of them.

The main thing I would recommend is avoiding the vacuum mounted products out there as they just don't stay in place well and contribute to messes. Especially avoid the red plastic ones as they are not worth the money. at all. Go for clamp on models instead, metal screens, readily available parts for replacement, and do comparative price shopping as they vary greatly.

Dave

I like my roma but agree with Dave the suction does not stay put and several times I almost lost the whole load of blackberries. my counters were installed without a place to clamp so I just have be very careful.
kim