What kind of airplanes do you have? I can understand wanting attitude
indication redundancy in a Bonanza, but it's overkill on a Skyhawk.

Do you have redundant attitude gyros? I've seen more of those fail
than dry pumps, never mind wet.

There are two basic approaches - tapping the intake manifold (which
means full throttle is no longer available if you want vacuum), and an
electrically driven backup pump (which adds weight). Decide whether
you want to carry the extra weight around all the time, or whether you
want to limit yourself to partial power when the vacuum fails. Both
systems work.

I think that if you really feel the need for redundancy, the sensible
solution is replacing the T&B with an electric AI.

Michael