Put it back up on eBay and sell it to someone else (so they can throw it away)? If you want to maximize your auction, I have a near-mint box (only opened once) I'll sell you.
Presumably, the seller either used the positive in combination with a Polacolor neg to do chocolate Polaroids, or bought it in a similar manner.
Could one possibly use the chemical pods from two 4x5 Polaroids of corresponding type, plus a sheet of fixed-out photo paper as a dye receiver? Yeah, sure, two 4x5 would give half enough developer, and four packets costs more than the 8x10 this was intended to salvage. And then the resulting print would probably need a coater you don't have because 803 is coaterless. Never mind.