You can draw up mechanical components in Autodesk Fusion, OnShape, SOLIDWORKS for Makers, or FreeCAD, and send STEP or STL to PCBWay or JLCPCB in China for manufacturing(note that export restrictions may apply if it's literal rockets or otherwise dual-use/controlled in nature).
PCB mounting outlines can be exported from above 3D CAD and imported to EDA tools such as Altium and KiCAD; KiCAD is fine unless you're doing DRAM or PCIe. Same PCBWay and JLCPCB takes your design, and optionally assemble PCB with parts for you.
That should take you to first 2-3 working units at ~$500 and up to few dozen beta units with zero initial cost and much inflated unit costs, and I guess beyond that involves significant human resourcing and networking problems outside of PoC hardware scope.
You could try a battery powered phone charger since it's a "relatively simple" first project. The big hurdle for learning these types of tools is usually "What buttons do I press to create the output that I want.
For the electrical side, there are plenty of schematics online that you can try to copy or use as a starting point. And the CAD side can be a simple box with snap fits. I'd recommend OnShape if you're just starting out since it's the lowest barrier of entry, but Fusion 360 is also good. All in, it should be <$150 for the PCBs + Components + 3D Prints.
After you get the satisfaction of seeing your device charge from something you made, then you'll start getting the itch and find more excuses to make things.
I'll follow your recommendation and try the simple stuff. Looks like OnShape is right up my alley. All very exciting feels like I'm "programming hardware" !
PCB mounting outlines can be exported from above 3D CAD and imported to EDA tools such as Altium and KiCAD; KiCAD is fine unless you're doing DRAM or PCIe. Same PCBWay and JLCPCB takes your design, and optionally assemble PCB with parts for you.
That should take you to first 2-3 working units at ~$500 and up to few dozen beta units with zero initial cost and much inflated unit costs, and I guess beyond that involves significant human resourcing and networking problems outside of PoC hardware scope.