What is the singular possessive form for rizals?

Answer 1

There is no word in English spelled 'rizals'.

There is a proper noun Rizal, a surname. Proper nouns are always capitalized. The form, Rizals, would be two or more people named Rizal, a plural proper noun.

The possessive form for the singular proper noun is Rizal's.

Example: There is a monument to Jose Rizal in The Philippines. Rizal's monument is located at Rizal Park in Manila.

The possessive form for the plural proper noun is Rizals'.

Example: The Rizal family believes in education. All of the Rizals' children attended college.

Answer 2

The singular possessive form for "rizals" is "rizal's."