WE had to either wear safety vests or the lime green/orange safety tee-shirts on our driving course. I chose the tee-shirt route. I ended up buying Gilden (mentioned in another thread) they last pretty good if washed warm or cold and dried on low heat. I've got some that are over six or seven years old, neck still tight, etc.
In terms of hi-vis, they aren't nearly as good as a vest, but if you don't want to wear a vest.......
I used to get them at either Orschlen's or Tractor Supply. Recently, I bought a couple of red ones at Northern Tool.
Just in case your interested.