Are there still any insurance companies providing coverage for upcoming flights out of Singapore?

Short answer, no. Negotiate with the agency to postpone trip on a later date.

Most travel insurance policies have a general exclusion that excludes compensation for major travel event which was publicly known at the time the trip was booked, or when the insurance was purchased, whichever later.

One of the major travel event is pandemic as declared by the World Health Organisation (WHO)

Since WHO has declared COVID-19 as a pandemic on 11 March 2020, hence it is unlikely to get insurance coverage to this end.

https://www.who.int/dg/speeches/detail/who-dire...

With this in mind, I will suggest for your parents to work out an alternative solution with the travel agency.

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