I have my BS in Biology and I went through alternative certification to become a certified high school biology teacher. I was hired by a school system in NH that was willing to endorse me. This basically means that they just appointed a person who would serve as my mentor. There is a whole list of things that you need to prove you can do, most of which you accomplish by actually teaching. I had a lot of previous experience substitute teaching and volunteering, so the certification process was fairly easy for me. I made a 4-inch thick binder to prove myself, and voila, I was certified. It was really more of paperwork for me than anything else.
I later served as dept. head of the science dept where I helped other teachers go through the alt. process as well. I am sure it varies by state, but in NH there are specific alternatives geared toward teachers who want to be certified in what the state deems "critical shortage areas". With your background it may be a good move to try to teach science rather than elementary ed, if you want to try this route.
Please feel free to email me with questions you may have. The alt. process is very inexpensive and I think it is your best shot as far as being the easiest, cheapest, and least stressful.
Good luck!