Good drivers aren't, "...looking for work". It's sort of like saying Emily Ratajkowski is trying to get laid - we don't have to look because we get more offers than we can count without looking. The problem isn't finding a new place to advertise. The problem is what you're offering in the ads you have now. What sets you apart from the hundreds of other ads that get posted every day?
Most drivers have a short list of places where they want to work while they're happily working for their current employer. That list of employers is the first place they look if they need to. Why take a chance on an outfit you've never heard of? Your best bet is to take care of the drivers you have now. Pay them fairly. Let them drive good, well maintained trucks and don't micromanage them. They will tell other drivers and your name will get on driver's lists, eventually.