My son is 10, but when he was born I wanted primary colors too. I had purchased a basket basinette that had a fabric lining with zoo animals that I really liked but it was in muted colors. Then I found the same fabric in the other color way! And it was red, yellow, blue and green! I made a quilt, bed skirt, crib bumpers and curtains with a valance. I have since sold the extras, but the crib quilt I will keep forever.
Keep looking. You'll find what you need. And - the Thousands of bolts website now has a quilt preview area where you can design your quilt and "plug in" the fabrics you choose so you can see your quilt before you buy the fabrics.
Don't be afraid to use fabrics that have the right colors but not necessarily a child theme. When they're cut into blocks you never know how they'll shine!