PASCO's WA-9607 kit is the version of a Chladni plate most physics departments own. It contains a 24 cm square plate, a round plate, 0.8 kg of extra-fine sand and a sand shaker. Drive it at a resonant frequency and the sand migrates off the antinodes and settles along the nodal lines.
Two practical points. First, the kit is only half a system: PASCO lists the WA-9855 Wave Driver as a required accessory, and you will also need a signal generator to feed that. Second, PASCO does not print a price. You add the item to a cart to request a quote, which is normal for educational suppliers but makes budgeting awkward if you are a studio rather than a school.
If you are building your own plate, this is still worth reading as a specification: plate size, sand grade and the fact that the sand is supplied by weight.