The shorts seem like they'd be fairly easy. But some SIMPLE white shorts, rip the pockets off with a seam ripper, sew on some purple bias tape, sew them back on, and add the button. (It'll be a lot easier to add the button afterwards, though it might look a little stranger. Oh well, no one will be able to tell unless they have their head in your crotch.)
Alternatively, if you can't sew, buy some fabric paint from a store like Michaels. Any craft stores in your area should have them. I paint shoes, and fabric paint works really well on clothes-type fabrics (cotton and such... Not so much leather, so this won't work if you're going to buy some white leather shorts.
). It also keeps the fabric fairly moveable without a lot of chipping. IT DOES, HOWEVER, look a little worse than sewing if you do a sloppy job. But back to this... Lay some tape over where you don't want to be getting paint on, or you're likely to make an odd brush stroke that goes out of the line you want. And unfortunately, white fabric paint doesn't always fix the mistake, and sometimes makes it look worse. After you've painted your purple, wait for it to dry, then you can either hand sew a button on (My recommendation... Though it might not handle a washing machine afterwards), or just paint over the purple. Oh, and make sure to wash the shorts before you put the paints on.
And for one more half-assed method, for if you really don't care how it looks but you want to get it done, use a sharpie. Color in a button first, then move up to using purple, then line the button with black.
Good luck! I was thinking of going as...err...that one reaper with the corset on. 8D But I can't sew gloves onto sleeves yet.
