You can get "Car Siding" at any of the BORGS, might be special order at the one near you. Where I am it's standard fare, and all of them have at least one width. Folks use it to make a half wall, and usually cap it with some type of chair rail, or similar. I used to do these all the time for people, and in more than one case it became the camouflaged door for a small storage space. It requires ducking, or maybe crawling into it depending on how tall you make the half wall. The car siding is just tongue and grooved material of SPF, and it's easy to leave a section hinged from inside, and using a magnetic catch at top and bottom, also on the inside you don't see hardware, but a firm push on the panel, and the wall suddenly opens. Further camouflage it by putting a smallish piece of furniture like a small table in front of it, and folks veer out of the way of it so they don't hit the table. The lines in the siding allow the cracks to be invisible, as it's a wall entirely made of cracks. Make the top just under the chair rail, and looking directly at the wall it's invisible, kneeling and looking up it's hard to see if you cut it well.
Thing to remember is drawers are rifled through, cabinets that are obvious are opened, but at the end of the day people breaking in looking for goodies don't like to stay for a long time. Averages I have heard from LEO's are 2 to 5 minutes max. If they walk into that room, they won't spend the time to find it.
cracks disappear more if the cracks are near the same color as the wall.