my suggestion is to get a new one. If you attempt repair, it will be obvious and only temporary. a new pc shouldn't cost too much (pennies per pound).
FYI: I know that Belden Brick and Supply carries this stone and can engrave as well. they are in GR on Leonard somewhere.

if you do try to use an adhesive, try using Pavetech retaining wall adhesive. this is flexible enough for the outside freeze and thaw conditions, yet is made to bond concrete and masonry materials together.

Thank you for your advice. I think I'll check further into repair, since a replacement would cost around $150.00.

Since it is only 3/4 inches thick I would look into attaching it to a piece of wood or placing it in a metal or bamboo frame. Sandy

How about gorilla glue? They claim its perfect for this, although I haven't used it. They have a website that gives locations for where to buy it.

Hypertufa has a thread on elmer's pro bond and gorilla glue that might be useful:

http://forums2.gardenweb.com/forums/load/hypertufa/msg1219380820413.html?10