Kiln Shelf for a large kiln

[GetGlassy]

I am in need of a new shelf for my 42" X 28" kiln. I currently have a fiber board that was treated with hardener. It cracked and has a few gouges that it needs to be replaced.
I've researched found vermiculite boards, Kaiser boards, and fiber boards but have no clue on which one might be better. Anyone have suggestions or pros and cons of the different types?
I would also like to buy one local but I don't have too many options so alternative suppliers would be welcomed too. Like is a vermiculite board for the kiln the same type used in fireplace backing? I have a fireplace store near that I could see if they had something that would fit. Any other options?

Thanks for any help!

[Bert Weiss]

My recommendation is to get an HD grade fiber board, 24" x 48" x 1" and cut it down. Do not rigidize further. You can get these nearby you in case lots of a few boards. Google refractory boards and look for the designation HD (high density)

Unifrax makes an LD board 42" x 48" x 1". I don't think they offer HD in this size? LD boards are easier to dent and to break.