Doesn’t have to be a thing you bought. Just some thing you didn’t have but then once you did it expanded your scope of actions.
The first obvious example that comes to mind is a car. Plenty of drawbacks to prevalence of cars, but being able to go where I want when I want, and far away, is very transformative.
I’m interested in other examples of things that aren’t just useful, but that open new possibilities.
It’s all of the above. Sometimes it’s researching in the form of looking around on sites like printables.com or thingiverse to see if someone else has solved the problem already. Scanning is an option too, but it’s tough to get good results with DIY approaches. The barrier to entry is kinda high in terms of money or expertise. When all else fails, there’s CAD. Computer Aided Design. Make it yourself with measurements and some trial and error :)