You already pay for a data vendor. Maybe it is a regional provider, maybe it is your own internal service. Either way, "we'll add it to the roadmap" is not an answer when the campaign is going out next week.
Any API enrichment lets you configure any REST endpoint as an enrichment step: URL, method, headers, authentication, request body built from lead fields, and a mapping from the JSON response back onto the fields you choose.
Set it up once as a profile and reuse it across segments and workspaces. It behaves like any other enrichment — run conditions, ordering, run logs, and per-run cost all work the same way.
If the vendor answers asynchronously, that is handled too: the step polls until the result is ready rather than failing on an empty first response.