Although you probably picked the *worst* subject to misplace all of your resources, don't panic! All will come well! Just try your best to find them of course.
In the meantime, I can let you know what to include in the proposal or at the very least, what I did for mine.
1. Description of Preliminary Research
This is an outline of the topic you intend to research and basically, your reasoning for choosing it. Linking your reasoning to a contemporary historical event doesn't hurt either. Though not absolutely essential, I'd recommend including the main historians you intend to use as well, it makes the whole proposal look more thorough.
2. Inquiry Questions
Here, develop a preliminary thesis that can you think can be answered. The trick is to not make it too difficult, but also maintain a level of sophistication befitting an extension topic. Also, you need to formulate several more smaller and targeted questions that get to the heart of the historical issue you're studying. I'd recommend at least 3 of these.
3. Areas and Texts to Examine
In this section, you essentially talk about where you're going to gather your sources from. It's a good idea to broaden your search beyond the Internet, the State Library of New South Wales, for instance. Whether you actually use sources from there isn't as important as including them in the proposal (although it's likely to help, especially if you pick an obscure topic) but nevertheless, it shows you're thinking about the historical issues surrounding the logistics of your research. If possible, I'd maybe mention some of the main works that will be important to your argument and how you'll examine them.
The last section will need you to state how you'll actually examine the sources gathered. This includes the way you'll examine and interpret the sources and if applicable, the kind of historical school you'll use to examine them. It's imperative to mention something about the context of your sources and how you intend to approach this issue in your research.
Hope this helps! Let me know if you want me to send you a copy of my proposal if you're still stuck. Good luck!