Your research proposal may be a part of your dissertation, submitted in advance, or submitted as a separate piece of work.
You may also be required to write a research proposal as part of a grant application.
You can and should use your dissertation supervisor as a sounding board as you develop your thinking, although beware of bombarding them with enthusiastic and/or panicky emails.
It’s usually better to ask for a meeting to discuss your ideas, rather than trying to have a discussion by email.
You can always find a sector, study group, or other unique element that will make the research worthwhile, even if others have done similar studies before.
Thinking about your research topic, ask yourself it is that you actually want to find out?
By the time you have finished developing your research question(s), they should be tight and carefully defined, including a clear idea of the sector or area of study, study population, and what someone will know after reading your research.
Once you have a topic, and research question(s), then you can decide on a title, which should broadly cover your research question(s) and summarise what you are going to do.
As a general principle, it is better to research a narrow topic in more detail than a broad one in very little detail.
Start to write up your research proposal as you read around your subject.