I started making my own bras about a year ago, and now even the thought of wearing the store-bought kind makes my skin crawl. It turned out the itchy, prickly feeling was a mild reaction to synthetics, and the ones I make are cotton, so they don't itch. It took some tweaking to get the pattern right, but now they fit perfectly.
I used a modified bodice pattern, shortened, with an elastic band right under the bust (cased in cotton of course). If I wore it over my shirt, I'd probably fit in at the ren faire.