I understand your concern and I am sure that most of them donot know how to get their own unique url. Because, I was having the same question myself last year. That's when I stumbled upon allmytweets.net
Ever since then, I have been using
allmytweets.net, for obtaining the urls of tweets. It's really a great tool for those who do twitter bounties as it lists all your tweets in a single page in seconds. Use this site, and you'll be able get your unique url with your username for your retweets.

I am sure this answer will help many members here.