Okay, so I toyed with Behance: right-click the image and do "Inspect" to open the Elements Panel. It'll have that image's info highlighted already. So just click the drop-down to see more URLs for different sizes. Open one in a new tab.
I also learned a trick though: Just save the image to a Moodboard. Then go to that board, and just open in a new tab from there. So that might be quicker too.