There is aproduct marketed that is called CAtaline Seawater. ***** and a few other shops sell it and its just plaiin so called filtered raw seawater. Kind of pricey. My lfs also sells bulk saltwater, which they make up with RODI, and sell cheaper than I can make it for, but I usually still make my own. There certainly is nothing wrong with either premade or make your own. Synthetic is probably the most widely used type though. YOU are checking the replacement waters paramters before using it I hope, and not just assuming its ok to use right from the dealer. If its the stuff the shop makes it can vary up or down in PH and SG and may need to be adjusted prior to use.
