I'm not necessarily looking for a magic bullet solution. It's more this is not really a solution at all. All it is, is just treating a symptom. And rather poorly at that.
Also, even if we did move forward with this, how are we going to increase the reflectivity? And where? The only viable option is to paint roofs white since it can significantly reduce cooling costs in the summer. But outside of that, there's no realistic option.
There is also the fact that trying to reflect the light back into space means reflecting it through the atmosphere a second time, giving it a second opportunity to heat it even further.
And a giant space mirror is not practical either. The resources that would go towards that could have easily gone towards more effective solutions on the ground.

Significantly more effective solutions would be to reduce our reliance on cars in western countries (simply switching to EV's is not enough); switch to greener power sources like wind, solar, and nuclear; redesigning our products to last longer and to be more repairable; etc.
If you want something a bit more direct to donate to and support, you could check out environmental programs. I, myself, donate to Mossy Earth. They focus on rewilding and re-establishing ecosystems throughout the world. They also have a Youtube channel where they post about their projects along with updates. If Mossy Earth isn't your thing, I know there are many other groups out there with like-minded goals. Find those groups and support/join them if you can.