I don't need them to be nearly as strong as you'd need with mules. They'll be carrying a max of 100lb. They don't need padding, either, as their fleece protects their legs. The main thing is adjustability. Male llamas have their testicles sticking out the back so you have to be careful to keep straps away from them.

“In a time of deceit telling the truth is a revolutionary act.”
― George Orwell

It's not over when you lose. It's over when you quit.