In-And-Out Convertible for Car Pool Buddy?

[jessicallyn]

We are carpooling for nursery school and I need a recommendation for a convertible carseat for our Car Pool Buddy to use in our car. Here's the problem: I can't leave the seat in my car all day- I need that space for my other children later in the day. So, it's got to be popped out after each morning's trip. Here's what we need:

-easy install/uninstall
-small (40lb. weight limit)
-relatively lightweight

So, what seat would you not mind putting in and out EVERY DAY?

PS
Price is flexible because if easiest seat is expensive (but of very good quality) our baby can use it next year after he outgrows his Keyfit, and until his sister passes down her Decathlon.

Thanks!