If you have a particular project to support, ask a dev if they can offer a "support contract" (even if that only means "clients can send me, the developer, an email if they have issues and I'll reply within 3 business days, I'll also take care of releasing at least once every 6 months"). That way there's something for the finance department to work with.
Once the dust settled, do the same with the next project.
Yeah, this ends up being compelling from the business side as well. If you have mission-critical systems running on OSS software then it is absolutely worth it to have access to the maintainers in case you run into serious issues or need a bugfix prioritized.
From the maintainer side it can be a bit tricky though. Typically the finance will want to pay another corporation, so the maintainer would need to create some sort of legal entity to bill with. The other potential issues would be around legal liability in case something goes sideways. You run the risk of getting sued if you don't provide a level of support that some corporate client is expecting.
Once the dust settled, do the same with the next project.