Sam's Club offers its members the Dyna-Glo Delux 125,000-BTU Liquid Propane Portable Forced Air Heater, model no. RMC-FA125DGD, for $129.88 with free shipping. (Non-members pay a $12.99 surcharge.) Except for the mentions below, that's the lowest total price we could find by $7. It can heat up to 3,100 square feet and features electric ignition and safety shut-off.

Note: Amazon, Target, and all have it for about the same price with free shipping.