Any amine oxide in which the three R groups attached to N are different is by definition chiral. But maybe what you really mean instead of "chiral" is more something like "enantiopure"?
In contrast to the sulfur atom in sulfoxides, the nitrogen in amine oxides does not have a free lone pair. So while sulfoxides could invert and be stereochemically unstable because they have a lone pair, that inversion is slow so they are generally stereochemically stable. In contrast, inversion is not possible with amine oxides (why do you think?) So if you can obtain one enantiomer of an amine oxide, it will be stereochemically stable. You should be able to find several examples of chiral amine oxides (for example, several proline N-oxide derivatives have been tested in catalysis.) They're just not used all that much, except for pyridine N-oxides, because they tend to be not so stable, especially on heating.