Kids booster seat???

I need a booster seat for my 7 year old son to ride in the back of a convertible (97 Cobra). I'm looking for a high back with head rest/support, but something very simple that doesn't look ridiculous in the car with bulging pads, crazy colors, etc. Safety is certainly important, but does anyone have a recommendation for a high back booster that looks "subdued"? I'd also like to spend under $100 if possible. The best I've seen so far is the Evenflo Big Kid LX.

Thanks for the flash back! That was me in my 97 cobra conv. In 1997 with my two boys and my 8 year girl.

Haha, that's great. I'm looking forward to making some memories with my son in this one and eventually passing it down to him some day.