All I can suggest is eBay, if you cant find one, then go to eBay usa, should be one on there. Freight may be expensive though...
If it was me, I would make one, but then it would not be chrome... You possibly could buy chrome springs somewhere and modify the bar that will fit inside the spring to hold them and the seat, paint just that section black as it will be covered by the chrome spring?
I'm not even sure that makes sense! :roll:
Luke.