I wouldn't bother with wire shelving.You can't be sure what sort of toxins(may be labelled as non-toxic to humans but still toxic to hamsters,so non-toxic is by no means a reliable way to determine safety!)are in the paint so it just isn't worth the risk.
However,DIY platforms can be made to custom dimensions using wooden dowels,Elmer's glue(not just any glue,this is the only glue I've found so far to not use animal parts in their glue and publicly state so),and hamster safe untreated wood.You can also make a popsicle stick rail or edge,which can be done with the standard apple sticks or willow sticks or similar sticks sold in most pet stores
