I suspect the Open-Source cleaner called
Retr0bright would probably work. The purpose of this compound is to reverse yellowing in ABS plastics, but I suspect it will also deodorize based on its ingredients.
By the way, how badly does one have to smell to have it soak into plastic ? or How long did the stank-infested clothing sit on top of the sewing machine before anyone did something about it ?
All I can conclude is that smell must have been epic.