Hi Elzane, welcome to the forum.
My son is 24months and until recently I drove a Hilux single cab (have recently upgraded to a double cab cos it was getting a bit tight with the two of us plus shopping, etc!). My son uses the Safeway Voyager car seat (R1300 about 14 months ago I think) which worked well in the single cab front seat. It's for 9 - 25kgs so it should last a while. It's not the cheapest seat, but also not the most expensive, and it seems sturdy and safe and comfortable.
Because the seat is in the front seat in a single cab, I think it's important to have a good one for safety reasons, although I don't think the huge differences in prices is always proportionate to the difference in quality (ie with some you will also be paying for the name). I would suggest taking your LO with when shopping for seats to see that she's comfortable in it and can't easily wriggle out of it. Also ask the shop assistants if you can take it out to your car to see that it fits well.
I hope you come right.