Well the easiest way of building your own livewell would be to use a big cooler box or you can buy those big black square boxes from Makro. Buy an outdoor shower pump from outdoor warehouse. They 12V. Then buy yourself some plastic pipe. Make small holes in the first 30cm of the pipe. You can then use a big bolt or something to block the pipe at the end. Then just bend yourself two hooks that you can hook over the one side of the box to hold the pipe. How it works is that you dump the pump in the dam to full your container. When you have reached the desired amount of water disconnect the pump and then drop your pump in your container. Hook the plastic pipe in your two hooks and turn so that it sprays water at around a 45 degree angle. So all you doing is using the water in your livewell and spraying it back on the service of the water that will create oxygen. Now on hot days. Just take some frozen 2l coke bottles and dump one of them in your container. By lowering the water temp the fish stress a little less. You can also buy stuff from most tackle stores that will help with the stress of the fish but best bet would be to go to a fish shop that sells koi’s and buy some salt from them That works just as good.
I will have a look and see if I still have my pumps and pipes. I know the pump was stuffing around so you might have to replace that. But at least the rest of the stuff are there