Only place I could find the sling and centre plastics were from Mad Amusements (Slow boat to China)
Ordered the 23/8/12 - Still waiting for any details on shipping,despatch time etc 
They show the slings as out of stock now - hopefully the ones I ordered were the last one.Showed in stock when I ordered.
Maybe only option you have is scan and make.
I will be scanning all mine before i put them back on the machine, fortunately all the other plastics are OK