I would recommend Ozean on Amazon. You can contact them on whatsapp and get all your doubts clarified and then place order on Amazon. They have outsourced installation services in major cities which you can check with them before placing order. The spares are very cheap.
I replaced an aging (12 years old) ION exchange under the sink RO (Zero B, I think) with the one Ozean has on Amazon. I replaced it myself. I have now bought a commercial grade RO for Hydroponic gardening purposes.