Ebay
Craigslist
It since you have 1, take it to a metal/welding shop and see if they can fab 1 for you.
Someone just got a pair made for $34. Wasnt on a Starcarft (SeaNymph I think) but end caps are nearly identical to an SCs and the new pair turned out great.
MichaelP used to make them out of aluminum, but is casting in urethane now. Sells them on ebay.