Stucco alternative for a small section of a wall?
I did something similar with a stucco house I owned where I closed in a window opening to create a shower. I framed in the wall with and installed rough-sawn cedar plywood. The texture coordinated with the stucco nicely. 

You don't want to install the plywood flush with the stucco. It'll look like a bad patch. You want it set back a bit like it's a design accent. Maybe 1-2". 

Caulk the plywood to the stucco and then prime and paint. If it's not in a very wet location it'll last many years, after which you can overlay a new sheet if necessary.