Adding a wireless 'bridge' to an existing wired network?

Current Setup:

1x Netgear Rp614v2 Wired Router
3x Desktop PC's connected via ethernet cat5

Want to Add:
1x Wireless device

-------------------

What is the best device to use that I can plug into the last remaining ethernet port of my router that will act as a wireless "bridge" between the wired router and the new wireless device?

I do not wish to go through one of the desktops instead of the router as this will result in needing that desktop to be 'always on' where as the router is always on anyway! I have also read about some wireless kit working with dumb devices and some not.. Would my router be a dumb device?

I believe I am after something like this Gizmo!

picture: > picture of setup <