Prior Tax Year Programs

I would like to purchase and download 2020 tax year programs in order to create duplicates of the returns I previously filed using a non-TT tax preparer professional.  Once duplicated, my data through 12-31-2020 will be ready to "carry-in" to the 2021 tax prep programs.  The data is a bit involved related to depreciation, deferred revenues, investment basis, etc.  I'm willing to purchase the 2020 programs (personal and corporate) so I can be assured of the process for completing 2021.  How do I purchase, for downloading, the prior year programs?  Thank you.