I realize that Amazon isn't the solution for Sri Lanka (or I assume so), but here's a system made in China that would seem to address your problem:
https://www.amazon.com/Simran-AR-3000-3000-Watt-Stabilizer-Transformer/dp/B000E636BU/ref=pd_sim_23_5?ie=UTF8&psc=1&refRID=5H56X9T2CRSF61B983R2
I tried searching on the product name (/Simran-AR-3000-3000-Watt-Stabilizer-Transformer), but it only came up in Amazon for me. Perhaps you could find a direct link to the product availability in your area.
Cheers!
Andy
