I’ve never seen one of those but it looks like it uses three small valves similar to the one Groco used in their SV series seacocks. Here is a link to the SV seacock owners manual. https://www.groco.net/media/file/file/s/v/sv-series.pdf
They haven’t made the SV seacocks in about thirty years. I don’t think you’re going to find one of those manifolds. The Reverso VA-3 manifold might make a good replacement. https://reversopumps.com/va-3/