I haven't reached the quest where it is given to witchdoctors but by the looks of the wiki its not in the crownshop
Thrifty Tristan Thatcher Lvl 59 Swashbuckler
Hi there Tristan, I have some good news! The Serpent Auger will (or at least should) become available in the Crown Shop once you have reached and completed the Chains that Bind Storyline Quest with your Swashbuckler. I purchased the Serpent Auger from the crown shop on my Buccaneer, so I know that other classes can obtain her, once completing that quest. She's a pretty powerful Witchdoctor with the Mournsong Power, which comes in so handy for farming lower level bosses and taking them out without having to move. It seems that the WD class has fewer in game, storyline and side quest companions to choose from, so I purchased her and some of the other Crown Shop ones to better balance out my crew.
It's possible that the wiki hasn't been updated with that information yet and that could be why the Serpent Auger doesn't show being available from the Crown Shop.
By looking at your level, it seems as if you should be fairly close to unlocking her, so good luck to you with that quest and getting that Serpent Auger.