Firstly iron-on should never be written so closely to heat transfer. You'll upset a lot of people insinuating they're the same.
Iron-On: You make these yourself. They print our on special transfer paper, avalible in any stationers. They're for inkjet printers, although I hear there are now colour laser options avalible somewhere (I have no idea how they work, given the heat during laser printing....the ink must reseal on the backing paper....which makes me think they would fall off in a tumble dryer).
These are the cheapest and easiest thing to produce. they are also essentially a "novelty" product, for your own home special events, birthdays etc....you can't sell these...people will send them back to you disgusted.
There are no other options with can be applied with a home iron.
Heat transfer: This is a whole range of differnet methods, from special inks you can buy for the home, to getting vinyl, plastisol, etc transfers made externally. You need a heat press to apply them, which will set you back anything from $400-$2000.
Neither of these are screenprinting, and so a professional screenprinter can only provide them if they're also a transfer maker.
In terms of where you can get them made, it depends where you are.......where are you!
A forum community dedicated to T-shirt merchants, professionals and enthusiasts. Come join the discussion about graphics, commerce, dyes, prints, collections, guides, displays, styles, scales, equipment, accessories, reviews, classifieds, and more!