Your first step will be to add the custom font you want for your drop cap. (mybookcave.com)
If you have ever used a Kobo e-reader, likely you are familiar with the ability to change the type of font you want your e-Book to use. (goodereader.com)
When adding fonts, you put whatever fonts you want in a folder on the Reader (it's not really a hack), and then add a bit of CSS code to the ebook so that it knows to retrieve those fonts from the folder. (blog.the-ebook-reader.com)