writing a paper as an independent researcher
First point - don't force it. Getting ideas for academic papers comes over time and has to be a natural process. The more you try to get good ideas for papers, the more unnatural the process can become and the less likely you will be to come out with something worthwhile. 

The best way to get a good topic is just to carry on reading around in your field as you normally would. At some point you may well come across a topic or a research gap that needs to be filled and one which excites you and stimulates you at the same time. That is the point where you can start planning your research. 

Bear in mind that a good research article topic can take time to discover. It can be weeks - or months - before you come across something worthwhile and that you feel you can turn into something research-worthy. You don't necessarily need anyone else to do this with, but you do need natural drive, enthusiasm and acumen in your area. If you have these, you will come across a topic and be able to write about it and conduct research effectively. But don't search too hard: writing academic papers should be a natural process and you'll find that something will present itself soon enough.