Rose, why would you want to use your electric heater outside?
Have you tried Houston Heaters dot com? That's who is in your link. Maybe they can help you?
The best interior heat is provided by the old-fashioned radiator heaters. Warm, even, dependable. Just are not esthetically pleasing to the modern home owner, but if offerd, I'd take them in a minute.
"Remove far from me falsehood and lies; give me neither poverty nor riches; feed me with the food that is needful for me. Lest I be full and deny You and say, Who is the Lord? Or lest I be poor and steal, and so profane the name of my God." Prov. 30:8,9