Hello,
I believe that the 8255s are easily available in the market. Atleast, I found plenty of NEC's chips available.
Comming to connections, I would like to know how you are doing your connections. If it is DATA & ADDRESS bus model then you connect Data Bus (PORT 0) to the dataport of 8255 (dont forget Pull Up resistors if you want to write data to the controller.i.e. you want to use the 8255 as O/P also.)
If you are not using the controller in the DATA & ADDRESS bus form, then simply connect the P0 of 89C51 to Databus of 8255 and 4 Lines of P1/P2/P3 to the Control pins of 8255. The reset circuit of 8255 can be easily made using appropriate Capacitor-Resistor values, so that when ever the systems is restarted, the 8255 is automatically reset.

The default value (of ports) when 89C51 is reset is HIGH (1).

Warm Regards,
Sriharsha.

PS: Please correct me in case I am wrong.