Just a thought, but you might also want to try placing your eggs in a carton to hatch. Some have said they think that all the rolling around can somehow adversely affect that hatching process. Worth a try.
I found ours in the area where they sell screens for windows and weather stripping for doors and windows - there are alot of different ones the brand I got is the Accurite - it was not that much money. also I am using a water wiggler ( you know those cheap toys filled with water that kids can sgiush - mostly found at the dollar store ) I can take a picture of mine if it will help you.