If you are looking for 10g because of an old application, consider that (the current Long Term Release) offers powerful migration tools. You can often move 10g data to 19c using Data Pump (expdp/impdp) or Goldengate , allowing you to run your data on a secure, supported, and high-performance engine.
After downloading Oracle Database 10g Release 2 (10.2.0.5), follow these steps: Oracle Database 10g Release 2 10.2.0.5 Download NEW
If you manage to secure the media, keep these hardware and OS requirements in mind for your legacy environment: If you are looking for 10g because of