As previously mentioned home depot, lowes, or any hardware store should have the needed pvc piece parts. You will also need a saw to cut the pvc pipe, I use a table saw but a hacksaw, coping saw, or just about any wood saw will work. Also you need pvc primer and glue to bond pvc together.
Figure out have you want it to fit together, cut the required pieces of pvc and test fit everything before gluing... I have re-piped my filter pad twice in three years. Plan on spending 6 hours your first time working with pvc. If you ever want anything pvc re-piped the second time will be much much easier and quicker...
I have attached a less than desirable picture, but I am out of space here so the quality sucks. Hopefully you will get the idea.