Hello and welcome to the forum. Wow, you have a rare early Mauser pocket model in .32 caliber. I like the way you refer to it as a 1912/14 Humpback as it is usually referred to as a 1914 Humpback when my research has revealed that they were made between 1912-1913. You have an early one, the 819th one made. They are rare in that less than 3000 were made. The highest serial number I have recorded is 2825. Because of their age and rarity finding an extractor may be impossible. The only way would be to find another example in poor condition and scavenging the part from it but there are problems even with that because it would be very expensive and hard to find one as described with the correct extractor. The extractor on most, not all Humpbacks is different on the early examples, like yours, than it is on late Humpbacks and the model variations that followed. Making the part, from a later extractor or scratch is a better possibility. You would need to find a master gunsmith or expert machinist to do the fabrication. That said, you have a very desirable and collectable example as is and depending on why you want to repair it you may want to consider other options. Are you looking to repair it to shoot it or do you just want to restore it? If to shoot, you may want to consider acquiring a common variation.
Regards,
