When I measured it I figured I needed an automotive grade weatherstripping that was at least 1/2" tall. I found "Front Rail Seal 5 1/2 FT" on Amazon (
http://www.amazon.com/gp/product/B00...?ie=UTF8&psc=1) for $12.50.
I cut the strip in to then measured the size I needed for the area from the Logo to the inside edge of the headlight on each side. Works great.
You could get by with something a little smaller, if you can find it, but I'm pleased. I had enough to also replaced the little inadequate weatherstripping that Toyota/Scion provided for the outer sections too while I was at it.
No whistle, should be long lasting. Oh, I taped it to the paint just like the OEM instructions for their pathetically small weatherstripping pieces - that way any movement/rubbing will not wear through the paint.
Hope you enjoy your deflector!