You can find good chain there, and some stainless steel caribiners (spring snap-in, when spring snaps back out, the thing is locked into a closed loop). If you want to be classier, you can even find stainless chain, but it is not as easy to find.
You have to watch the state regs, however. some require that the chains be crossed (seems stupid to me) underneath the tongue. I made mine just long enough to comfortably snap the caribiners onto the trailer hitch safety chain eyes, and made sure I can turn left and right without interference. Main thing you want is to hook up the chain, then unhitch the trailer and make sure the tongue will not hit the ground. If you get that right, you are good to go.
There are other safety checks to watch out for. Here in alabama you need a good fire extinguisher (type 3 I think, good for gas, oil and electrical). You also need a throwable life preserver. Not to mention proper lights for nighttime use if you are out after dark. A noisemaker is required here but a good whistle will meet that regulation.
Some states require trailer brakes if the boat/trailer exceeds some weight…
