This is the question related on how many quantities you need. We can divide the quantities to some ranges and suggest the process accordingly.
 
If you just need a few pieces or less than 50 parts, you can consider make them through vowin.cn' target='_blank'>rapid prototyping method: by 3D printing or CNC Machining.
 
It is convenient for you to build your part via prototyping, but before going ahead, you should consider what the parts would be applied for, whether it needs to work under pressure or force/weight, etc.
 
If you need hundreds, rapid prototyping may not cost-effective. Making a rapid tooling and go ahead with Rapid Injection Molding process should be the best solution. Then you can consider overseas China mold maker.
 
For many different parts, you can have your mold maker to build one or several family mold to cover all items. As the small volume you can use the soft steel such as Chinese P20, NAK80, S136H etc as the mold steel. But of course, you need to take the part’s material and finish into consideration. These will cause the different steel selection