We have this one, that we use for our 45lb ACD mix.
http://www.discountramps.com/dog-bike-trailer.htm
It could hold a much bigger/heavier dog. The price was right and it works fine. It’s like a jogging stroller, where the front wheel doesn’t turn, so you have to lift the front a little around turns, not a problem with a dog of this size. It converts to a bike trailer without a lot of fiddling around, which is also handy.
Our old dog likes to go for walks, but can’t always make it home, so I’m often pushing the empty stroller “there” and she’s riding in it “back”. She likes it, she willingly gets in it when she gets tired and sore.