I got mine from summit racing the 4 slot one there is still just a bit more then the one you found. Although on mine I didn't use a 4 slot I thought about using one originally, but I couldn't find any way I liked to mount it in the original spot then I thought wait why mount it there and not under the seat in the little plastic pan, or in the pans spot, didn't feel like making a bracket to mount it, so I started going up in fuse counts hoping to find one that would span the entire length then I could separate each electrical section into individual fuses, make my own blown fuse indicator, and store spare fuses.
Got to about 10 fuses and noticed that I would have to get a 100 fuse fuse block just to span it, so I opted to mount the fuse block in the tray itself and still have a small storage spot, as well as keeping with a 8 slot fuse block for blown fuse indicators which I never installed instead now it works great for storing extra fuses. The 3 needed fuses 15A main, 7.5A headlight, and 5A tail light along with 2 spare 15A, 2 spare 7.5A, and 1 spare 5A.