IMHO, if you don't want a regular sized Aussie either 1) improve your odds by choosing a small puppy from small (but still within standard) parents or 2) if you really can't handle anything up to standard, don't get an Aussie! I'm not a fan of huge dogs but I'd rather take my chances than support breeders of a designer breed that's currently "in". A 20 pound Aussie isn't going to have much in common with a real Aussie, all those great traits have been sacrificed for size. You'd be better off going for a recognized breed from responsible breeders.
eta: I still haven't looked at the site Laur posted - my internet is absolutely crawling tonight. I also might be coming at this from a different viewpoint as other people because 1) I've grown up with great standard Aussies and 2) I'm a horse person and like I mentioned before, Mini Aussies have replaced the Corgi as the big horseperson dog, so I'm especially seeing them gain popularity.