Using Google Shopping search today I found the WD 4TB Portable External Hard Drive For Apple Mac listed as $63.93 at my local Office Depot. Clicking on the link to the Office Depot website showed the price as $89.99. I decided to go into the store to see if I could get the drive at the lower price. While it wasn't with all the other hard drives on display, I showed the Google page to a store employee and with the item # 6106235 they were able to find one on lock-up in a back room.
Note that this will work fine for Windows as well -- just needs to be reformatted with NTFS.
(Or just search for "Western Digital 4TB USB" in Google and click shopping.)
YMMV depending on location and store availability. The usual Slickdeals wisdom applies: Do not call to ask if it's in stock / at the lower price.
Link for reference: https://www.officedepot.com/a/pro...-Portable/