This weekend, several of those mounts are back, so if you missed one in the past, this is the perfect time to visit the item shop and correct that oversight. Dawn and Phantom Ferrets, Flying Rune Discs, Witch Brooms, and even Ruzio the Expedition Donkey are back in the item shop for the weekend.
But it gets even better: there's a brand-new mount available this weekend as well. The Ground Gryphon is the latest addition to the item shop, and just like the others, it comes bundled with a seven-day, 30% mount speed buff potion. You'll need to move fast if you want to grab any of these; they're only available through Monday the 28th.