Your letter inquiring about [subject of inquiry] was brought to my attention.
While we manufacture a vast assortment of [products], none of our models fit the description which you provided.
We have never manufactured [subject of inquiry].
You may wish to direct an inquiry to the following distributor, whose firm has been in existence for many years and who may have the answer you are seeking:
____[name of firm]____
____[address]_________
____[city,state,zip]__
I am sorry that I cannot be of more assistance to you.