I use a shop light i got at menards (big box home improvment store) that hangs above a provides light for 3 of my tanks. I dont remember how much it cost but i am pretty cheap so it must have been reasonable. Check out what they have if you use your imagination you could come up with all...
I have had multiple females in the same tank a number of times and I am in the process of setting up a new one as we speak. Ill post detail as I get closer to putting it together.
The old copper pennies are still plenty common just look for the ones before 1982. I have never heard of that trick but it would be really cheap to try it out.
I would check your water, having more then one fish die at a time would indicate to me that there is something wrong with the water not the other fish.
Davyj