I think if you haven't already, look at the program's website to see what they say about this. Some programs say if you've been out of school for 5+ years (or something similar) that work related references are acceptable. I'm sure they understand that not all students go to graduate school straight out of undergraduate coursework.
With that said, I would definitely ask someone who is familiar with your work ethic, ability to complete tasks, etc. (like a supervisor as you mentioned). You could always set up a meeting to discuss your plans, how this degree would help your career, etc. It's a slippery slope b/c what if they are not ok with you leaving? Or, would you be planning on staying w/the company during/after?? But, if someone who is supervising you can speak to your qualities, I think that would help a lot.
I agree with contacting a previous professor and showing them your CV, work sample, etc.
I would even contact the program you are applying to and ask them what they are looking for in terms of references. It will show that you are truly interested and that you understand the competition and want to stand out!
Good luck and this is just my opinion, of course.