You can use a list comprehension (Python 2.6+):
y = ["{0:0>2}".format(v) for v in x]
Or for Python prior to 2.6:
y = ["%02d" % v for v in x]
Or for Python 3.6+ using f-strings:
y = [f'{v:02}' for v in x]
Edit: Missed the fact that you wanted zero-padding…