Honestly, unless you have a serious need to make a massive number of stamps, I would stick to tracing and hand cutting. Heck, maybe even a very fine CNC router would be what you need if you want something (in theory) cheap.
If you want to get fancy, perhaps you could go for an additive construction method. Flexible 3D printing filaments (no experience, just an idea) might be a cheap solution if you can find a good 3D printer that can use it.