Hi, die casting is usually for a hundred thousands parts, hence the expense of having a die made.
For a 100 parts I'd use lost wax casting.
This is in the region of DIY capability with a small electric or propane furnace for the melt, whereas the diecasting set-up is not user friendly due to the technique of getting the molten metal into the die etc.
There was a design in the Model Engineer magazine some years back where a guy made a small press like device for making small diesel engine pistons in aluminium alloy.
The device had a vertical plunger that was removed to pour the metal in and then the plunger was quickly reinserted and a lever used to force the metal to fill every detail in the cavity.
As the cavity was for pistons, the design was fairly simple, with machining to finish them off later.
If a complex shape was being considered, then it would need someone with an EDM set-up to spark out the design, or a pantograph machine.
If time is no problem then there is a small EDM design, that is also in the Model Engineer, and is capable of being made and used to do quite serious work by the average DIY'er with some electronic knowledge.