I make my own. There's at least one product out there but it's something like $20 a bottle and you can make it for pennies. Here's a recipe:

For 150ml of (distilled) water: 1.35g of salt 1.8g of iota carrageenan A drop of polysorbate 20

Heat up the water to close to boiling, add those things, shake it up, and there you go.

Note: That was supposed to be in line with the product that was tested, but I've found adding more water makes it come out of the nose spray bottle thing better. It's still pretty thick, just not a complete gel. Perhaps there's another type of spray bottle that would be better.