The few times I have needed a heat lamp around the house I just used mine I had for my snakes I don't use anymore. Growing up we used them for our chickens and rabbits. Those from the feed stores are probably made for animals but I know there are others that can be found at hardware stores that don't have the holes. Usually in the painting area or bulb/light area. People may try to save money and buy them as they are usually really cheap and not know they are missing the holes.
The ones you get at the pets stores are usually a bit better because the dome is not as soft so they do not bend as easy as those from the hardware store. But then maybe most have holes now. It has been a long time since I needed to buy one.....having so many. I have even given some away to new keepers I was helping out.