The least expensive straight purchased new is the Dovo, at $80. In your price range, you are looking at a used razor. The best place for you to get one is Whipped Dog:http://whippeddog.com/products/find/straight-razors-1
You can buy one through the classifieds at StraightRazorPlace or Badger & Blade, but you may or may not get a decent razor at that price. Whatever you do, don't buy one off eBay - "Caveat emptor".