The piggy-bank icon should work, but you need to add it without any prefixes in the SVG icon subset site setting and in the JS override functions.
The Pro icons are not included in core, so for the Pro-only pig icon, you can use the plugin suggested by Jay above, or you can create your own sprite. Make sure you look at the example SVG sprite file linked in the OP, the sprite needs a specific structure with symbols and IDs (and then the ID is what you use in the JS api calls).