Just letting others know, that recipe is not safe for vaginas and you'll end up with a nasty infection.
Bad Dragon sells a lube known as Cum Lube that is stringy, white and thin enough to shoot through a squirting dildo. You can also use Liquid Silk, a white lube, for a thicker cum substitute, it will still go through a cum tube just fine. I like to mix up Liquid Silk and Probe Thick and Rich to make a thick, creamy, clear and white cum substitute. Another substitute is J-Lube, which starts off as a powder. I haven't tried it yet, so I can't comment on it, but I know plenty of people use it for this.
The syringe that the Squirt comes with will likely be difficult to clean, you may want to replace it with some sort of syringe that can be taken apart and cleaned properly.