"Riviera" or "Rivieras" for plural

To distinguish a riviera from a Riviera, it should probably be lowercase:

1. a resort area along the Mediterranean coast, extending from Saint Tropez, in SE France, to La Spezia, in NW Italy. See Côte d'Azur.
2. ( often lowercase ) any similar coastal resort area: the Florida riviera.

No less than four results come up when googling "plural of riviera"; two are irrelevant. This site suggests rivieras as the plural form:

The plural form of riviera is rivieras.

And the other site does as well:

Rivieras is the plural of Riviera

I would, in the absence of contradiction, follow English instinct and simply say rivieras, now that it's been naturalized to English.