Welcome! Looking forward to seeing the new tank setup. Most of the LFS around town have either DI or premixed salt water available for purchase if you want (eg Cuttlefish and Seahorse). A lot of folk just run their RO/DI output directly into their tank and wait it out but that can require a bit of extra tubing. Someone would probably lend you some extra tubs for water if you can’t go straight to the tank. Just a few ideas.