booster seats

My kids have been in the backless boosters for a while. Technically, they are both legal size to ride without one in my state...but I prefer them to stay in a booster as it is recommended. Anyhow...I have backless boosters in my van. However, dh just got a Ford Ranger extended cab. So, the seats in the back are TINY. They are smaller than the booster seats...so, of course, the booster won't fit right. I've been searching online and in my books for something that might work...but can't find anything. Anyone know of a booster that might work in those little seats?