you can buy the actual valve, something like this, then all you need is the tubing which you can get at most hardware stores. that would be the easiest way to do it
or get even cheaper something like this.
11802 Fill and Drain Kit
might even be able to find at walmart or somewhere local. then you swing by lowes home depot pick up the hose and adapter and you are set.
the only other question you will have is do you want to attach a gravel vac to the other end or not.
The one thing to watch out for with a diy setup is making sure the hose is sturdy. I tried a garden hose and found it collapsed in vacuum mode. It needs to be a thick walled hose to work best.
can i use the same python for my FW and SW tanks?