Custom gs500 tailpiece/ single seater

[Streetslayer]

Does anybody know what the stubby seat is called that can go on the gs500? It looks sick but I haven't found one Anywhere yet but it looks awesome!

[Bluesmudge]

I'm not totally sure what you mean, but I think you are referring to a "cowl." On a GS, it can cover the rear portion of the banana seat to create a solo seat look. Or you can buy a new solo seat. Nice ones for sale here:
http://www.whaccessories.com/GS500Accessories.htm

other options are to find the tail and seat from another bike and swap it over, which might involve modifying the subframe.
Stay away from a company called cowl tech, they make a bad product and have horrible customer service.