Need Help on Growing medium?

ok since i lost all of my growing sponges that come with the AG from my last grow i just wanted to know if there's another alternative that i can buy at walmart

Not really, but you can get rapidrooter by general hydroponics and they fit right in the hole. Is what I am using now and working great. I am not using the AG pods anymore due to the plastic gets tangled up with the roots and is very hard to get them out without shocking the plant and cutting a few. The rapidrooters have no support but fit in the AG holes tight and you can use some sticks like long stir sticks or something else for support when they get bigger. The rapidrooter things cost like $15 for 50. they are ready for seeds and have nutrients for the seeds in them. I fill the AG to just tough the bottom of the rapidrooters.