Many Japanese teachers and schools have created free workbooks. These are not the official books but supplementary sheets. Search for terms like:

Digital PDFs allow you to use Ctrl + F to instantly find specific kanji, English definitions, or readings across all 50 lessons. How to Buy Official Editions

The Minna no Nihongo Kanji PDF is a remarkably well-designed bridge between spoken Japanese and written literacy. Its greatest strength — strict alignment with a single textbook — is also its limitation. Once you finish Minna no Nihongo II, you will need to move on to native materials (news, manga, novels) because the PDF’s reading passages are artificially simple.