If you want a more decayed zombie Supes, take a look at the GW plastic zombie sprue. There's one torso/leg combo that can be painted as Big Blue's union suit complete with cape - the torso is wearing what looks like a shirt or sweater hanging over its shoulder with the sleeves tied at the neck, you just file off the knot and voila, instant cape, no other conversion required. Add suitable zed head (there's one with the right hair, even) and a pair of no-weapon arms and you've got a nice rotten Last Son of Krypton ready to paint, and he's even more shambolic and rotten looking than poor Bizarro there.