try glide floss or silk by oral b. Its like ribbon
There are alternatives to floss- although if you cant get floss between your teeth yuo might not be able to get interdental brushes between your teeth either.
Check out Tepes on the internet - they are sold on eBay too - far better than floss where they can be used.
there is no "alternative"-- flossing is the best way to preven between the teeth decay and gum disease. Have you tried waxed floss? have youtried gliding the floss down and then sliding it out the side? Have you had a professional cleaning which may remove deposits that may be catching the floss? you can use things like rotodent and other $100 gizmos but there is no substitute for flossing. if you can't get the floss in, see a denist and get an explanation as to why.
I usually recommend Glide Floss for tight contacts, it works well in those areas.