Get yourself some replacement screen window netting, staple it to a couple of broom handles, and hit your local waterways. Hold the net downstream of you, reach back and kick over some stones and dredge up the bottom and you will have all you need in pretty short order.
It would be even better to get the kids out there with you when you collect, but I understand the logistics (and probably legal issues) would likely prevent that from happening.
"We fish for pleasure; I for mine, you for yours." -James Leisenring