You could create a single wordpress page with a PHP or meta redirect to the final URL. Then each of your blog posts would link to that single page. It would work, but I reckon that once you got past about 50 or so outgoing link pages it would get pretty hard to manage easily.
A better alternative as it would be more managable would be some customised PHP and a database – but it is obviously more complex. You would put the outgoing link in the database and then display the contents of that database record in each blog post where you want to show that outgoing link. Doing that you would have an admin area to edit links in the database.