As far as commercial products go, we've had luck with home chemistry kits. Also, optics (projectors with little slides, binoculars, magnifying glasses). And hom

As far as commercial products go, we've had luck with home chemistry kits. Also, optics (projectors with little slides, binoculars, magnifying glasses). And home insect kits (caterpillars to butterflies, keeping ladybirds and feeding them aphids) went down extremely well. Otherwise, I just take my chances when I can. When there's some interest in some random thing, I just try and run with it and encourage further scrutiny.