I've never seen Clonex at my local garden center, but it's not the only brand that works. (It is very popular though, so you can find it online if you wish.) Any rooting agent (powder, gel, mix) will work. In fact, it's not totally necessary. You can get a cutting to root with just water. If you're in a pinch, just use whatever they have at Walmart/Lowe's/Home Depot.