How do I reblog a post from one blog to another under the same login?

I have been posting personal and startup stuff in my own Tumblog, but now that we're setting up one for our startup, I want to kick it off by reblogging the posts that relate to the startup. Both Tumblogs are accessed under the same login, though, which means it won't show me a "reblog" option when I'm looking at my own posts.

Is there a way around this, or do I need to create a new account and add it as a contributor just for the purpose or reblogging myself?