So i do buy most of my fry foods on line as rainbows tend to need quite small fry food, however, in the times i've run down to petsmart for an item or two, they usually do have at least one type of fry starter food.
I've never bred rams, but have had a couple and given they're not huge fish, i don't quite know about starting them on frozen brine and blood worms, it seems a bit large for me for fry...maybe live newly hatched brine shrimp, but the frozen stuff is large and you'd have to grind it a fair bit to start with. I can't get rainbows onto that until they are several weeks old. I tend to go golden pearls/artificial rotifers, newly hatched brine shrimp at about a week, then start the frozen brine shrimp/bloodworms at a few weeks depending on how fast they grow.
That's just my five cents, and again, i have no experience breeding rams. I can't say i've ever seen any of the LFS's stock fry food, but that's just what i've noticed. Try petsmart and see what they have. The one i saw that had it (and it was months ago) was the one next to the aurora mall. Each breeder seems to develop a regimen that works for them. Its ideal to feed fry frequently, but the reality is that most people aren't at home all day, and you can get away with twice a day just fine. I have had eggs get into an established tank and had them survive for weeks without any supplemental food. Fry aren't always as fragile as we think they are.