2008 Prius

Do you have HIDs?

If so, Philips D4R Xenon HID Headlight Bulb, Pack of 1 : Amazon.com : Automotive directly from Amazon (not a 3rd party seller) I think should be a safe bet. Amazon's listed at Philips Car lights, Lighting under Where to buy.

There a whole bunch of DIY threads here on it, but I warn you, it may not be easy w/o removing the front bumper cover. For me, the metal clip came off and I couldn't get it back on blindly w/so little room so I had to eventually remove the cover.

 

Changing bulbs is not fun on the Prius. The safest route is to take the entire bumper off the front and then remove the headlight to change the bulb. Some folks have also successfully changed bulbs without taking the bumper off, but it is a bit tough. There are may threads and youtube videos to walk you through both these procedures.

If you are handy with tools, you could DIY a good HID projector kit. I am not talking about the cheap conversion kits. I just (in the last 30 minutes) finished a retrofit. Details are in this thread. One of the best threads on a full kit retrofit is in this thread.