Yep - here is my thread when it happened to my '95 diesel. Sucks, doesn't it?
http://www.500eboard.com/forums/showthread.php?t=6936&highlight=star
At least it wasn't my 500E. I just bought an OEM star off eBay - they seemed to have good pricing and there are several sellers to choose from. Don't know the part number but here is one.
http://www.ebay.com/itm/Genuine-Mer...ash=item27dc4009d1:g:3SgAAOxyRhBSsyVJ&vxp=mtr
Of course Lionel or Naperville (Napierville?) might have a better deal, but at the time I did not check with them.
Edit - using Gerry's link it looks like Naperville (mboemparts.com) has it for $37 - with free shipping that seems decent.