I got two different brands at Tractor Supply, "Horse Health" and "Durvet". The ones I found were clearly labeled "Ivermectin 1.87%", and do not contain any other active ingredients. The inactive ingredients are mostly corn oil. This is a standard form of the product, and it is what you want. Dosage is exactly as labeled on the product, just use your weight to dispense the correct amount.

Some products from the same brands are different active ingredients, or a mixture of ivermectin and other things. You don't want those.

Remember, we are not trying to deworm ourselves (which can probably be accomplished with various drugs), we are trying to use ivermectin specifically, and this just happens to be a way to acquire it.

Note that I picked mine up in store a couple months ago, I have no idea if they still have stock... :(.