That is one of the hardest parts to find for the little colt 380's.
Try Jack First's as I have heard he may have a few. I have been on the hunt for a spare for several years and not found one. Last time I checked Jack First's (maybe a year back or so) he was out and I just have been keeping an ear to the ground to try and find one.
Maybe a 238 extractor would fit?
10mm and 357sig, the best things to come along since the 38 super!