Whats the name of that story....?

Story by UserName

Hey guys maybe you can help me, I've been looking for a story I saw a long time ago, I think on asstr or nifty. It involves an amazon shemale that kidnaps a man (maybe on island) and forces him to service her. He is surgically modified to accommodate her and if doesn't service her he could die due to some sort of genetic reprogramming. Thats really all I remember. If anyone has any idea what story this is or where I can find it it would be lots of help!