If there is an RV parts store (Parts66, etc.) or a boating supply store (West Marine, Bass Pro, etc.) in your area, you might try removing the old fittings and taking them with you to get something that is a reasonably close match.
Side note, it's odd that one fitting is labeled "Water Only" and the other "Potable Water Only."
They should BOTH say "Potable Water Only." The only difference is that one lets you use city water directly, the other lets you fill your fresh tank with city water.