The best alternative mattress materials to the Purple Grid are gel memory foam and latex foam paired with pocketed coils.
Both gel memory foam and natural latex are very good at temperature regulation, and the pocketed coil core found in a hybrid mattress can help give you the bounce and responsiveness you'd get out of the Purple Grid. Plus, pocketed coils are breathable to keep you even cooler.
If an all-foam mattress is more your speed, go for a latex or plant-based memory foam one. These will still maintain a lot of the cooling power and responsiveness of coil mattresses without the reduced durability or bounce.