Heh...not absolutely certain that it's not on there...but I think Underwear was only on the initial UK release. Not sure if it would be on any subsequent ones. It wasn't on the European versions I don't think.
"Slide" = You get the normal cd, in the normal case, with the normal label, but there's also a copy of the label printed on a sheet of cardboard which then "slides" over the top of the CD case. Typically found in Japan, for whatever reason. It's nothing special..
"Why not try" shoving card into your printer to design your own special "Slide" edition sleeve? You could even add a multicoloured patchwork cardboard cutout of yourself to the group!