I would suggest Minature Market and GameNerdz. They have run out of Special Alternative covers, like the Tyranny of Dragons 2019, before and restocked. I usually order my special alternative covers, which are usually ten dollars less on their website for new DND 5E books, and they have been great and reliable. They even have the Tasha's Cauldron to Everything alternate cover up for pre order as well.
I would also say for future reference: Always pre order the alternate covers. That way you avoid any hassles or headaches.
Both options were available at my FLGS; I opted for the standard cover as I think the art on that one is more interesting and compelling than the special edition. Went the other way with the Theros book.