depending on how much you want, you may want to try a waterjet company who may stock it. Theyd cut to size.
as i said though, it would really depend on how much you needed as it is quite costly.
Hi just an update really.
In the end I was looking around Wilkinsons and they were selling photo frames in a sale for �2..50 each and they were the size I was looking for.
Two of them cost me less than a fiver with the reduction in vat as well.
I was delighted, I gave the frames away, so nothing was wasted.