I heard diatomaceous earth (food-grade) is a pretty effective way to get rid of them. And it's safe too if you have toddlers or pets. Can try looking for it on Lazada. Just have to sprinkle on the floor of the car and leave it till the all the cockroaches are dead.
The platform idea looks pretty nice, but removing the mattress to take things from the storage below is a hassle. I guess end of the day is whether you want to sacrifice the aesthetics or the practicality...