What other alternative can you do to get pregnant after having your tubes tied without having surgery?

Some data suggests that approximately 1 in 2000 tubal ligations may spontaneously reverse. More precisely described, sometimes the cut and closed (cauterized and or sutured) fallopian tube tissue ends aren't closed enough to stop the familiar path of a teeny, tiny, tenacious ovum or egg that follows a chemical trail to the uterin area during ovulation. If fertilization is facilitated in this unusual but possible scenario then (tubal ligation or not) pregnancy is certainly a potential outcome. Matthew David Black existencebeyondperception@msn.com
If the tubes were "banded" and not cut/burnt, the bands can loosen, opening the fallopian tube. This is pretty rare, and the likelihood of this happening depends on the material used.
You can't.