The closest one I could find was a 1979 yellow one the same size as mine with a lot more wear than mine and not as unusual as mine for $15.99 + $4.82 shipping : http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=170154400260&ssPageName=MERCOSI_VI_ROSI_PR4_PCN_BIX_Stores&refitem=250138593467&itemcount=4&refwidgetloc=closed_view_item&refwidgettype=osi_widget
As you can see by the scans, mine is almost mint and very special in color and design !
This is a must for a collector !
Shipping for this is $6.00