Can I buy them somewhere? I mean those, that separate different tiers. I can find round and square, but not else. Now I`m planning to buy hexagon and petal shaped pans, but can`t find same shape card boards. What do you use?

http://www.logic pic.com/ (take out the space)

Make you own hex board using cardboard or foam board.
Trace the outline of the pan on the board, add 2 inches (or whatever size you want) around the outside and then cut with a box cutter and a ruler.

Depending on the weight of the cake, use 1,2 or 3 layers taped together and then covered with the medium of your choice.