Hi userrussia,
These two words are not widely used. "Безызгибный" means "membranaceous" and "безызвозный", "with no carriers" (street, for example). "Безысходный" is the same tyoe of adjectives and it is more widely used, it means "hopeless".
Without the prefix "без" these words start with an "И", not with an "Ы". There is a rule in the Russian language that says that after the prefix "без" you can't use "И".
Best,
Yulia Amlinskaya,
Russian Language Teacher.