I went through this just last spring. We have had a H8080 with a 419 discbine head for a few years and wanted a 25' triple delivery swather header also. Ended up getting lucky and finding a HW345 with a 25' honeybee header. At least the heads and tractors are interchangeable. Was only a few $ more than finding a header alone. Could find lots of 30' and 35' headers but 25' is considered too small now a days.
It's about like finding hens teeth to put together a unit like that.
That is a rare combo but worth it to the right user. We found a used m205 power unit, a demo 16 ft disc head , and ended up biting the bullet on a new/old stock 25 ft swather header. Was able to get the whole shebang done because of decent salesmen at our local CNH multi location dealership (youngs)