I'm agonizing over this myself. Based my my internet research, it seems that there isn't a reliable 14" trailer tire made today. I have some Titan radial trailer tires now, but they're 10 years old, and not made anymore.
I'm looking at a higher load-rated 15" radial passenger car , in spite of what everyone says about not using them. Of course, that will require new wheels also...
Be interesting to hear what suggestions people have.