To build a lightsabre IMO takes a few basic things: Energy, Stability, Control.
In SW lore, the original lightsabre was connected to a power-belt worn by the wielder, as the amount of power required was too much for anything small enough to put in a hilt. Some of the more advanced sabre techniques were therefore not applicable - no spinning the blade about your person... getting tangled would be a surefire way to lose!
So given that we're not even close to making some Fusion based Duracells, it would be prudent to focus on the actual blade itself and forget the hilt for the time being.
The blade must be contained within some form of magnetic field, strong enough to repel other fields (so we get that lovely CLASH! (probably minus any sound effects), and of course enough to contain the plasma which creates the blade - lasers are useless here, you'd never generate one powerful and wide enough to cut through anything fast enough.
The plasma is generated as part of a circuit. In the lore, it's all done with focusing crystals, which Is possible now, given the right form of crystal and grinding tools. But my understanding of energy/plasma generation is non-existent, so I can only speculate how you would produce plasma and somehow focus it into a upwards beam. I do understand the concept of the confinement field, and that the plasma must be made to come back down to the hilt again, to complete the power circuit - the plasma itself is used to power the energy/plasma conversion, thus ensuring power is continuous. A small amount of energy is used while the plasma is visible, lost with light and heat, and when striking an opponent, but the majority would find itself back within the circuit.
My idea for a fake sabre in the real world would just be either a powerful laser diffused into a wide beam, or a REALLY powerful bulb, again, focused to travel upwards as much as possible, with a telescopic central core, like automated car aerials, with the mirror on the top - this should be sufficient to produce a nice looking beam.