Hello Craig. I have been collecting Topps sets a long time, what exactly do you mean by a sell sheet ? Is it an advertisement for a particular year of Topps cards ? Or are you referring to salesman samples, which are pre production cards with advertising on the back ? What years are you looking for ? Take a look at
http://toppsarchives.blogspot.com and see if you can find what you are looking for on it. Great site for Topps items no matter how obscure
Where in Texas are you located. I am in San Antonio