You will need an undergraduate degree before an MBA
You often don't need an undergraduate degree to do a post-graduate degree like an MBA - I didn't - if you can demonstrate long term, relevant experience. It would depend on the institution where you were doing the MBA, many offer this option.
The "work experience" option exists for a degree like an MBA, because the OP would have worked in a business environment for most of his career. There is an understanding that an undergraduate degree prepares you to a specific level and often work experience can teach the same level of preparedness to complete a post-graduate degree (note, that's your ability to study, not your preparedness to work in a specific job).
There are technology/management post-graduate degrees also, which is what I did, and I do not have an undergraduate degree, and that's never been an issue for me. For the most part it's been having a degree of some kind that gets the "tick" when applying for jobs, again at least in my experience.
You would often need to complete the initial graduate certificate (in my case, that was 4 subjects) with a specific grade point average to be able to continue on to the full degree.
And that was going to be my suggestion to the OP - not to do a full degree initially, look at post-graduate options that he may have access to as a mature-age student. Advantages include, there is an early exit point (graduate certificate, graduate diploma) and they are faster to complete, as there are less (but harder) subjects. In my case my degree was 12 subjects, the undergrad would have been 24... I finished it in 2 years, while working full time.
consider enhancing your portfolio with a PMP certification.
I completely agree - PMP or maybe CAPM if he doesn't have the PM experience to do the PMP straight away - and/or Prince2 (just do the foundations cert if you're short on cash). These are "quick wins" also, doing them is an instant line to add to your resume.