What frequency and voltage? Do you care about the DC behavior? Does it have to be a true (energy storing) reactance or can you use feedback like a gyrator circuit?
Anyway, the simplest solution would be a variac. Just use the output alone (protect the input plug so nobody get shocked) as a variable inductor. For a variable capacitor, connect a large fixed capacitor and use it as an impedance transformer. You will have to look closely at the current and voltage ratings to make sure you don't overload something.