It becomes more interesting to build your own and turn it into a 'BOO'!!! ;D
Just checked out the one at yamaha motor, it's not a case saver, just a chain guard to stop your shoes, clothes from getting in the chain. A case saver has a thick piece of aluminum between the chain and the casting.
Just make one, it's very simple. To get the curve of the case there just place tracing paper over it and then just simply stab the pencil through where the mounting holes are. To make the case saver part of it just cut a slab of 1/2 in. sheet aluminum or billet to the traced curve, and then dremmel out a bunch of hollow spaces in it so it can sort of collapse and increase the impulse time if the chain breaks. You can also bend a chunk of aluminum to the curve by torching it with propane and bending it over a pipe. Be cautious with the torch, aluminum will burn and turn to ash if it gets too hot.
I made one out of diamond plate. It was pretty simple just like boxhead said. I used some thin card board to get my shape and traced it. Then just cut it out dremmel tool. Once this piece o junk is back together I'll post some pics