Air handler in closet

I want to install an air handler in closet but the supply houses dont seem to carry a louvered door except a bi fold which I never cared for. They also dont have a louvered grill that is made to cut into a door. What do most people do now to get air to the air handler . I can order the louvered door if that is what other people are doing .I dont want to cut a return air out thru wall.

You have answered your own question. Some very nice filter return grills are available, but you don't want that. SO you need a louver door. Available at any good lumber yard. They might have to order it, but can get it in a few days.

Once you determine how many square inches of return you need, you could cut the door. You could use a conventional return grill on each side for appearance. You would want to box in the cut internally. Assuming this is a hollow core door, you need to beef it up around the hole.

Huh? Try a lumberyard, instead of the Big Orange or the Big Blue.