It needs to be built to NFPA specs. Non-combustible material spaced at least 1" off the wall with non-combustible spacers. Gap top and bottom.So how about something like this, with an inch of air space behind it, and a durock wall with thin brick?
Refractory Fiber Brick Liner 3 Pieces ‐ Herringbone- HB36RLH
For use with Kingsman HBZDV 36" Fireplaces. Traditional Herringbone Look. Back and side walls- 3 pieceshvacdirect.com