Want to be slightly more unconventional in your Dr. Horrible costume? Try being Groupie #1
Socks:
Gray and yellow rugby stripes, knee high.
http://store.americanapparel.net/rsaskfkw.html Shoes:
Definitely look like Kangaroos to me (cause I have a pair in purple/black), but I can't seem to find that color. They might be another brand, though since they aren't the cheapest shoes in the world, I would think any bright blue shoes and laces would be fine.
Examples:
http://www.amazon.com/KangaROOS-Womens-Lotus-Sneakers/dp/B000X47J2A/ref=pd_sbs_a_4http://www.zappos.com/n/p/dp/29661571/c/103857.html Shirt:
Bright or neon green spagetti strap cami or tank top with a "razor back" as it is called,(more of a neon yellow-green, for sure) with a DIY iron-on transfer of Captain Hammer's face. You can actually get the graphic from the JINX website where they are selling the official tshirts. You could just buy the groupie shirts they offer, but again... if you are going for on-screen accuracy, DIY is probably better. Iron-on transfers (for dark tshirts) can be found at Walmart, Office Depot, and pretty much any store that sells office or craft supplies. Ususally in the computer paper aisle.
Examples:
http://store.americanapparel.net/4358.html#i -->closest in cut and color, though doesn't have a razor back.
http://store.americanapparel.net/6311.html#ihttp://www.blankshirts.com/details.asp?style=DT202&color=Bright%20Greenhttp://www.oldnavy.com/browse/product.do?cid=7524&pid=563493&scid=563493022 Skirt:
This looks like a light denim skort to me, though I have no idea where you would find one. 80s fashions are back in style lately though, so there might be some trendy store selling them. Let me know if you find anything.