Second this. Add some food to get some NO3 to start reading. If your boicube has a bag of carbon &/or sponges that need rinsing, rinse those items in the new setup. It’s another way of introducing bacteria into the new tank.
Try searching for a Hirsch Pipe & Supply near your area. If your near the LA area, try Ellis Aquatics or I know for sure that Koontz Hardware carries a variety of gate valves.