You don't absolutely have to have a BSCS to get into the OMSCS. However, without it (or something like it, or equivalent experience) you will be at a major disadvantage and will probably not be successful. So your desire is the correct one.

-Regis University has a good BSCS online program. 8 week semesters, relatively inexpensive, ABET accredited.

-Regional accreditation and ABET accreditation are the standard for a BSCS program. Don't go to any program that doesn't meet that criteria.

You don't need a degree to get into AI/ML, you can study and learn it on your own. Udacity has courses to cover the basics of CS, edX has course from MIT and Harvard, etc.