I have the self employed turbo tax, but I noticed it does not do the 1120S for my S corporations. Where can I get that software, preferably online?

See https://turbotax.intuit.com/small-business-taxes

However, there is no online version of TurboTax Business (nor is there a Mac version - Windows only).

Sorry, You need Turbo Tax Business.

The small business program (TT Business) is for 1120 Corporation, 1120S Corp, 1065 Partnership or 1041 Estate/Trust returns and will not do your personal 1040 return.   It  is a separate program from the Desktop Home & Business program or the Online Self Employed version.

Turbo Tax Business  is not available to do online or on a Mac.  You can buy the Window's version here.  And you can have both TT Business and TT Home & Business (or any personal version) installed on  your computer at the same time.

https://turbotax.intuit.com/small-business-taxes

Desktop Windows System Requirements

https://ttlc.intuit.com/community/system-requirements/help/minimum-system-requirements-for-turbotax-windows-software/00/26175

FYI ... you will NOT need the SE online version of the TT program so you can just use the Premier if you have not paid for that SE version yet  OR  you can use ANY of the personal downloaded versions.  Deluxe if you need a state return and Basic if you don't ... that way you can save a few dollars.

AND  the 1120S was due 3/15/22  unless you put yourself on extension until 9/15/22 or are on a fiscal tax year.  So file ASAP since the penalties have been accruing since March.