http://fdiland2k23drdjqmxgmnjmzb47s3ildy5wyh5t4gk2tgjo3yfdffyyd.onion/kemono/thread/2.html
Honestly, though, if a Pixiu doesn't have a butthole or a peehole because it's "a creature that only takes and never gives", I don't see why they couldn't have a vagina. Especially with how in the manhua they're shown to be able to freely go in and out of each other's gullets, the Bixie impregnation theory weirdly checks out.
By the way, apparently multiple kinds of Pixiu are distinguished by their habitat.