Why do you necessarily need them to have a "side-firing woofer"? Are you referring to speakers that have powered, side-firing (pseudo) subwoofers? If so, DefTech would be one speaker to look into. Boston Acoustics used to make speaker like this, as well. But there are other speakers that feature powered (psuedo) subwoofers and they are not all side-firing.
If you want the speakers to specifically have side-firing, passive woofers, why exactly?
"All men are frauds. The only difference between them is that some admit it. I myself deny it."