Med schools are looking for "well-rounded" students. Forget the number of hours and just volunteer for all sorts of things. Do Habitat for Humanity or some other community service type thing and then find something else to do. Medical experience isn't really necessary for most schools. There are some, DMU comes to mind, who require a letter from someone who can vouch for how well you work with patients.... but most schools want to see you being involved with the community. That's all.
Keep in mind that there is no requirement for shadowing. Some schools do require a DO letter, but you need never shadow them to get it. All you need to do is meet with them and express your desire to be an osteopathic student. You might just get a letter that way.
You see, it's not a big numbers game. What you are trying to do is convince the med school that you are willing to give a part of yourself back to the community. Sure, thousands of volunteer or paid medical hours will never look bad... but it is far from necessary.
The way to get in is to do some research and find out which schools you might like to attend. Then, apply to as many of them as you can afford to. Make your goal to get interviews. No school interviews people that they aren't perfectly willing to accept. Once you have the interview, then you do what you can to sell yourself to them. Believe it or not, that's what they are trying to do as well. They want to sell themselves to you.
