Dear

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 am unable to be of more assistance to
you. Best of luck!