Small enamel missing on bottom of front tooth = Cheapest way to fix, replace? Products??

Cheapest way to replace, fix small missing Enamel chip on bottom of front tooth. Or, any do-it-yourself Products I can "paint" on/fix. I was even thinking like something like fingernail polish , just to keep it from chipping further away. 83 Yrs of age = past vanity point. On Medicare but No Dental Ins.