Thermal insulation is usually sold in rolls at the mall hardware (e.g. ACE, True Value).

Based on my experience with the Besta, underseat insulation is only part of the equation. You also need a good seal between the engine cover and vehicle body kasi malakas sumingaw ang heat sa edges ng engine cover. Kailangan may rubber weatherstrip talaga. Meron naman yung Kia, kaya lang may mga areas pa din na nakakalusot.