Hi I am sure the derailleur you need will not be too hard to find. depending just where you live one of your LBS should have some. ebay is a good source too. does your derailleur have a brand/model name? someone may even have one in the ISO/trade thread
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“One morning you wake up, the girl is gone, the bikes are gone, all that's left behind is a pair of old tires and a tube of tubular glue, all squeezed out"
Sugar "Kane" Kowalczyk