Does anyone know of a booster seat that will fit well in the seats? I have a 5 year old who's chomping at the bit to ride in "the race car". I have other booster seats for him but the bases are way too wide to fit down in the seat.....they'll cut the heck out of the bolster part of the base of the seat. I googled and found the one made by Simpson but $230 is pretty steep for something he'll be out of in a year or two and without seeing it in person I'm still not sure if that would fit either.

Anybody with a specific make and model that they know will fit?

Thanks!