How big of a manger are we talking about?
You could always cut down a shoebox and splay out the sides, laminate the inside and outside with wood pattern shelf paper. By the time you put in the hay and arrange hay on the outside, nobody will know it's shoebox.
If you want something a different size or more permanent, you'll have to find a friend who has some carpentry skills or learn how to make one yourself.
Good Luck
**or learn how to make one yourself**
That's what I'm hoping to do with help gleaned from this thread.
I mean...I can change a lightbulb, and hang pictures on the wall. I helped build a tree fort when I was a kid. Whatever boards and nails we could scrounge up wound up hammered into a tree in the woods.
I realize building a Shelter/Structure for the Nativity is a bit more involved, but I can learn. "Primitive" is what I'm looking to build.