I got one while buying a bunch of items. I think if you contact customer service before they ship your order, they will add the riser cable.
This is what I did. They will tell the factory in China to add those items to your order. A phone call or email will do.
Also, don't forget to buy ALL the extension cables for your motherboard and power supply. If your motherboard was like mine or @K D You'll end up needing extensions just to plug in the switches and power ports. Nothing was more frustrating than getting everything together and realizing "Shit don't fit right" and seeing you need an extra 2-3" cable.
Save yourself 2-3 days of wait time, order them NOW.