Dear

After checking with all of our other stores in the area,
I regret to inform you that I have been unable to locate
another [item requested] for you.

If you would like me to place a special order, I would be
most happy to do so.  Normally, it takes between four to
six weeks to receive merchandise ordered in this manner.
If this is your desire, please call me at your convenience
at [telephone and extension].

On behalf of  [name of firm]  I would like to thank you
for shopping at our store and if there is any way that we
can be of further assistance to you, please let us know.