Here are 2D renderings of some of the detail parts I have designed for my own modeling projects and friends. These and others can be purchased through Shapeways at my shop.
These parts were designed with SketchUp. In many cases I've put them on the shop on sprues of multiple parts, which are much more economical.
If you need a part, contact me. Not everything is practical for 3D printing, but I'll be happy to take a look. Plans are great, measurements helpful, photos essential.