Please help me oh wise ladies of style and beauty. I am neither stylish nor beautiful but I'm going to be a bridesmaid in about 7 weeks and have to buy my own outfit. I hate shopping so have stuck my head in the sand and not bought anything but even I am starting to get twitchy by the lack of a frock.
The bride is going to take me shopping if I can't find anything but the earliest we can get together is just 3 weeks before the big day which makes me feel even more nervous.
Wedding is not very traditional and is being held in a barn. Bride's only stipulation is that the dress be purple (a darker shade, not lilac). I am tall- 5 10 ish with 28 h boobs. Anything strapless or requiring no bra is absolutely out. Even the best scaffolding can't hold my boobs up without straps and I don't want to spend the day hoiking them up. 
Waist is between an 8 and a 12 depending on the shop. Legs are ok but usually encased in nice forgiving 70 denier black.
Budget is up to 150 but preferably under 100. There is another bridesmaid (who is as bad as me and doesn't have a dress yet either) but we don't have to match just both be in purple.
Any suggestions of suitable dresses gratefully received!