Another option, albeit a little bootleg, is to remove the tumbler, insert the key you'd like it to match, and file down the leaves that protrude. Before you file, cycle the leaves you have so that you're as close to a match as you can get. Provided a few are still sticking up when you remove the key, you won't be able to start it with a screw driver. It's honestly not a bad option.

__________________
1981 240D 4sp manual. Ivory White.