NFIP flood policies do not have aggregate limits. A per occurrence limit is not the same as an aggregate.
NFIP policies have per occurrence limits with no aggregate. That means, for each flood during the policy term, the policy will pay up to a specified amount. For each separate flood, the limit reinstates to the full limit.
An aggregate is different in that it is the maximum amount payable during the policy term regardless of the number of occurrences. If you have multiple flood events during a policy term, the aggregate will reduce by the amount paid and not reinstate to the full limit again until renewal. The danger would be having multiple flood events in one policy term and ending up with an inadequate limit.
If "at least as broad as NFIP" is the standard you are using, in my mind, an aggregate limit is not going to meet the standard. I write a lot of private market flood in my agency. We are seeing aggregates, but we won't use a market that insists on an aggregate limit for that reason.