you can get retweets to your tweets from retweettrader.com. This is a great source for to get retweets. Hope this will be helpful to you. Just have a try.
Maybe you can check out fiverr.com. For 5 bucks you can buy all sorts of things. Just do a search for twitter and see if anyone can help you out.
See Retweeters.us that service looks affordable and reliable. It's better to get natural retweets because you will get satisfaction yourself and you don't have to waste money to get retweets