I recently replaced my 55-gallon gas water heater with a 50-gal model.
I foolishly assumed the new model, being less capacity, would fit into
the sheet metal shed attached to the back of my house. Alas, the new
heater is wider and the old shed won't quite fit.

I've searched online for why to buy a new, pre-fab water heater shed,
and I can't find anything.

I live in Los Angeles. Do they have be custom built? Where do I go? Any
suggestions?

Thanks.