Connect 27" display to Apple Thunderbolt Display
What you need is a Displayport/DVI/VGA port and a displayport/thunderbolt port and since it seems you don't have a Mac with a second Thunderbolt port you will need to get something that will give you two Thunderbolt ports.

Once the question is framed that way (?) then it seems to me that the choice is one of the Thunderbolt "docks" that are often sold as a way of connecting a MacBook to numerous ports all at once via Thunderbolt.

There are numerous examples of such devices out there but you may end up with a lot of ports you don't need (USB, Ethernet, Audio, SATA, etc.) depending on which one you decide on.

I am not aware of any devices that are the Thunderbolt equivalent of a USB hub but perhaps other folks might know of something.