Solid State Backup AI

I'm part owner of a IFR 172E. Nice equipment, but no vacuum redundancy.
I know I can add a dual-rotor vacuum pump or a manifold-driven
alternate vacuum source, but I'd rather have an electric backup (in case
of engine failure). Electric pumps add weight and good backup electric
AI's are expensive. Does anyone have any experience installing/using
the new solid state gyros? I have an iPaq and handheld GPS, so the
"portable" units would be OK. One of the manufacturers has a panel
mounted unit, but apparently it can't go into a production plane. What
are the chances of getting a 337 for that if it is for backup only? I
can do partial panel, but I'd rather have the most capability that I can
get (within reasonable expense).
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