Here's a couple of places that sells brush seal, there are lots more:
Strip Brushes Standard Backing Sizes - Tanis Inc.
Brush Seals Custom Brushes
The Fuller Co. has some stock shapes and sizes, I didn't call to check but that's what their entry in the Thomas Register said.
I'd think that trimming the brush to ALMOST touch the tire would be the ticket. If they did touch, tho, that wouldn't help FE very much.