I appreciate this was posted around 6 weeks, but there seems to have been a stock refresh on the Xbox One version
Both versions are now showing wide availability in many regions.
PlayStation 4 Link
eBay Link (Xbox One)
"DEFINITIVE MAYHEM, REMASTERED! Borderlands: The Handsome Collection is the essential Borderlands compilation and includes the definitive versions of both Borderlands 2 and Borderlands: The Pre-Sequel, built specifically for next-gen consoles. PlayStation 4 and Xbox One customers will experience the absolute highest performance and highest fidelity graphics for any Borderlands game ever played on a video game console. For the first time in the franchise's history, play four-player split screen on a single television, all in stunning high definition. "