Maintenance specs on the 2015 Kawasaki Versys 1000 LT call for a change of the oil drain plug gasket with each oil change. I didn't change the gasket on my first oil change because I didn't have a replacement and the original aluminum gasket looked fine. It's not my place to second guess the manufacturer so I'll certainly make sure I change that gasket during each oil change going forward.
The part number for the gasket is 92065-97 and the size in mm is 22 x 12 x 2. Online prices range from $1.50 to $2.95 each. That's a little on the high side, but the real problem is that there's going to be shipping that could run $15.00 just for a couple gaskets. Unless you have a bunch of other stuff to buy it's probably not cost-beneficial to order these, or parts like these, online.
Your dealer probably has them in stock as mine did today when I stopped in. However, in a pinch, it's a standard M12 aluminum crush gasket that's available at any auto parts store for a buck and a half ... for two! I previously had picked up the Dorman, Oil-Tite gasket number 65290, which is the exact same gasket as the OE. OE gaskets pictured on the right in the photo.
Both gasket types are crush washers for a better seal. Below is a photo of a used gasket.