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!