Old ICs are harder to get. The sollution would be to make new ones. But now there is a alternative. The web page FPGA Arcade has developed an 28 pin module with an FPGA. This FPGA can be programmed to simmulate hardware. Arnim Läuger makes programs for this module and has now made a PLA for the Commodore C64. You can buy a programmed module or buy an empty one and program it yourself. You can find lots of other FPGA information on this web page too.