Where to start searching to find more radioactive minerals?
You can try using the locality list at MinDat. Go to places that are easily accessible to you and see what minerals have been reported there. If there's something radioactive, it will probably be listed there.

I would remind you that radioactive minerals are, well, radioactive. These things are dangerous. I strongly recommend you find a different hobby. I deal with radioactive minerals as part of my job, and this is not something that you want to do unless you really know what you're doing. I remind you that a lot of the early researchers who worked on radioactivity died because they did not use the necessary precautions.