It might be possible to stick a piece of wood of the right shape on there, but to hold the repair won't be invisible or as elegant as it is with the bent plywood.
I think the repair might cost you as much as finding another one of these online (maybe not on the expensive market places).
Cheers
Ernest
teakhound-- hand stitching an upholstery is actually a fairly easy thing to do, especially if it's just a bit in the middle of a straight seam. Would the entire back panel of the chair have to be removed? Even if that's the case, an upholsterer wouldn't charge the same amount to redo it it as he/she would to upholster the entire chair. And someone with little to no experience could redo it if it's just the area around the bolts. The only special equipment needed is a 2" curved upholstery needle and some heavy duty upholstery thread--both of which are sold at most fabric stores and will not cost more than $10 total at most.
Finding an intact leg is a whole other issue. I'd walk away, myself. (mostly because I've already taken on far too many projects like this in my life and I know how most of them ended up---left in the dust as soon as the next one came along.)
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