Parents help! Booster seat advice? Options

[bnr32celica]

So, my little supermodel has outgrown her carseat. She exceeds the height threshold, which means the seat is VERY uncomfortable for her. Her carseat was a combo seat that was good from birth to 3. Well, she is just about 3, so we did well. My problem is that I cannot find a high-back booster that fits the rear bucket. Right now, I am using a standard booster (no-back) which fits, but is definitely too big for my little supermodel. My parents gave me an older high-back which fits, BUT, it's older than 8 years old...which makes it out of code and technically illegal. My little one is #1, and if I can't fit her in the car safely, the car goes. I'm asking for advice as a last-ditch effort to hang onto my car, because I have bought and returned multiple car seats (and I think the people at Target, WalMart and BabiesRUs are starting to get annoyed). If I don't find a seat soon, I'm going to have to sell the car. Brands and model names are appreciated. In an ideal world, the seat would also be less than $50 as well. If you have pictures, even better (without kid is ok). I have the leather seats, but will be doing a black cloth swap soon. It also doesn't have to be a combo seat that disassembles to a no-back, because I will most likely end up replacing the seat when she hits the no-back threshold.

Never thought a car seat would cause me to have to think about selling the Celica, but like I said, my little one is #1.