If you are just starting out in manufacturing business and needs a prototype model for presentation to your would-be investors, then you can get the services of specialists in engineering one-off design. They can make use of cnc prototyping which can spawn the exact replica of the design you have in mind. Regardless of what type of material that your model will be made of, you can now easily find a prototyping company online that can make even a single model for you.
Whether it's made up of cast iron, stainless steels, bronze, aluminum, silver or ever plastic-based materials like PVC, cnc prototyping can provide it to you. But before you handover your prototyping needs to a particular company, you have to visit a couple of websites and ask for multiple quotations. Keep in mind that some companies do only large orders but can still accommodate your small order - with astronomical prices. So if you just want a couple of samples, then you need to find small prototyping companies that can take your order for as low as one piece - and still get a good bargain.
But the price should not only be your concern. The company should at least come up with printed sample using 3D model printer even you only gave them sketches so you can have a clear picture of the end product of your order. Remember that you can be thousands of miles from them so the best sample that you can have is to have them fax you the prototype printed on a 3d model printer. However, if you only send those in sketches or drawings form, it can be at a little off from what you have in mind. So it is always better that you send your order in CAD files like IGES, Rhino, STL or DXF.
To give you assurance that you are working with a prototyping company that has a credibility and not just does fly-by-nights that are just out to hassle you with a quick buck, you can run a thorough background check on them. Search for testimonials or do little investigative work. You can track down previous clients and asked them how their order went. Ask about the delivery date and the quality of the work. Ask about how meticulous they were in coming up the exact model that you have in mind. Remember that even a single model can cost a fortune especially to someone who's just starting out in the manufacturing business.