I did a Digi-Key search and found several possibilities: SN74LS245N (0 available), SN74LS245NSR (non stock), and DM74LS245N (non stock). They do not stock them but can likely get them.
Mouser has: NTE74LS245 (stock) and SN74LS245N (non stock), both DIPs.
Also Newark shows them as a non stock item.
A tip whem searching for digital ICs. The common logic families and many of the less common digital ICs have been second sourced by other companies. They are the same, identical ICs, often made from the original developers masks because many government contracts required a second source for parts. However, they may not have an identical part number.
When I search for an IC, I usually totally ignore any prefix and suffix. The prefix (SN in this case) is just the manufacturer's ID for that line of products. Hence the SN indicates TI's digital line and the DM indicates the exact same line in National Semiconductor's world. The suffix usually contains information on the package. there are many suffixes that indicate the DIP outline in general and variations for different package materials like plastic, ceramic, etc. By searching for a "74LS245" I instantly got all the versions of that IC and I could find a substitute in the package I wanted. If other specs are a concern, Digi-Key and the others have links to the manufacturer's sites for full spec. sheets.
I wish mechanical parts suppliers were as well organized.
Paul A.