Special shop called Tap Plastics.
http://www.tapplastics.com/product/plastics/plastic_rods_tubes_shapes/clear_acrylic_tubes/141
Need to have the exact measurments though. Have to plan out each row (as like each row behind the next will need to be higher than the one in front). So it requires some effort (need to measure your case width and height, as well as the rows etc.)
Jason is hooking me up next month with enough for all the Smash line. I still think the Acrylic Stairs are prob the best option for most, as they are well priced and already take care of the work for you. With these, you have to have the tubes cut and measured. You have to really graph out your rows with your case measurements. If I didn't have Jason helping me out, I would def not do it lol
Basically, depends on the lengths you are willing to go to pimp out your case. I'll be doing these + some special LED custom strips I'm buying. But that's all I'm going to do. I should just be happy with what I have now, because it looks really really nice (especially in person). But Jason and I are always teaming up off board, so he got me lured in