Any WordPress dev should be able to add them. They could reference the free extensions that do this to see how it is done. They’ are all documented pretty well so a dev should be able to follow without too much trouble.
And here’s a link to a demo plugin they can reference to see all the support custom field types:
I could do the work and I have time available in my schedule. Could you please contact me via the contact link at the bottom of the page with the details.
I look forward to hearing from you.