Convincing people is easy. Build a closed system, grab an inverter, sell power back to the power company, which in many places they are required by law to pay you for. Sell enough power back, you'll get attention.
The idea that demonstrating a net-positive process is hard is merely smokescreen tossed up by the perpetual motion scamsters. It's not. It's easy. It's as easy as it is to demonstrate that a gas generator produces power when you add gasoline and oxygen to the system. If you have a process that works, you can generate and sell power to prove your point and go from there. The fact that nobody can quite seem to manage this feat, despite the easy money it would represent if you actually had a solution, is proof enough that it simply doesn't work.
A system that pushed out a kilowatt and never stopped would be very easy to prove. It's only hard to prove something when you're sitting there fiddling with picowatts and arguing whether the power comes from the magic process or if you're simply translating magnetism into electricity or some other fiddly, on-the-edge-of-rounding-error sort of thing.
Also, any true net-positive process can be turned into this sort of thing, simply by feeding back the net-positive process onto itself. Any net-positive process should be able to produce a kilowatt, easily. (Arbitrary amounts of power, actually, but let's take something thinkably-small.) Again, the fact that they have to resort to fiddly little rounding errors is proof that they have nothing. Any interesting perpetual motion process would be able to power a nation, if it actually worked.