Convertible in a Prius?

[mars817]

I just saw there was a carseat forum on here and have been looking for a new car seat and thought I'd see what folks have to say.

DS is 5 months old and about 20lbs, his infant seat only goes up to 22lbs. I was going to get a Britax but when I went to buy it we discovered it doesn't fit in my car (had the same problem with infant seats..). I found a women selling a chicco 30lb car seat on our local yard sale site and was thinking about getting that to use for now but I'm not sure about a used car seat and that only patches the problem for now. Anybody have suggestions for what carseats that have higher safety ratings and would fit in a prius? We have to take a very unsafe highway to get almost anywhere so I want something that has the higher ratings. The recaro would fit but it is pretty tight and the owner wanted their car seat specialist to check it out before they would sell it to me anyway to make sure it was ok.