I've found a few good folk patterns here: www.folkwear.com/patternindex.html

how handy are you with patterns? I ask because especially with simple stuff it's not too hard to get the biggest pattern you can find, see what the size increments are and just add that many units to the outside of your pattern. I usually recommend getting some cheap muslin or cotton fabric to do a mock-up since every body is different anyway. I put the pattern over the fabric, and when i need to make it bigger just get a ruler and a sharpie and make some dots along the lines at where you think your size would be. remember to copy down those pattern notes too (arrows and notches and such) and when you get a good mock up, all tucked and let out in the right places, un-baste it and keep that as your pattern piece.