If the part you want is now obsolete, first go to the Cypress website to the Obsolete Parts Search page:
Cypress Obsolete Part Search
Enter the part number you would like to replace and see if there is a recommended replacement part.
In many cases, an asynchronous dual-port can be replaced with a similar device in a faster speed. So if you were using a -25 device, it would be safe to replace that with a -15 device.
For a device with no suitable replacements, Rochester Electronics (www.rocelec.com)is Cypress's authorized distributor for obsolete products.