Hydroponic stores, Home Depot’s Garden Center, even Amazon – anywhere that sells plant supplies. It’s not limited to weed.
If you’re looking for specialty pots, like large scale or fabric style, there are lots of online options for those as well.
And they also have “platforms” which raise your roots off the bottom of the pot. It helps reduce the plants contact to any garbage that sifts to the bottom as the plant grows. Our homie who posts those insanely purple plants all the time runs the company, so you can see the kind of dank he’s growing with it.
Hope that helps!