Just on principle, the wheel should be replaced, and paid for by the car driver, if you can find them.

I would take the wheel to the shop and see what they say.

Many Bontrager parts that come on bikes are not available to the after-market, but probably has something similar with a different label... The dealer will have something appropriate.

If you really want to search yourself, there are a few things to look for. I haven't tried looking up the wheel, but some things I would consider for a replacement. There are probably other factors, but these will get you pretty close.

1) Rim
a) size (both diameter and width)
b) Rim brake surface?
c) color
d) Profile (so it looks similar to the rear)

2) Hub
a) type (disc or not?)
b) color

3) Axle type (quick release/through etc.)

4) Spokes
a) Number of spokes and pattern I would go for what I wanted, not being overly concerned with what the old wheel had
b) Same color as rear wheel