I think the Saxon/Germanic ones might be a good option.
Playmobil’s Roman and Egyptian ship might be easier to convert (and can be gotten relatively inexpensively).
Thanks! I'll look further. The Nydam Boat may be an example, although its lines are different and the planks at the prow do not curve sharply upwards.
Yes, I have one of the Roman Playmobil boats, and must look for an Egyptian one.
Perhaps, I should just sell off my excess longship kits and buy something that is more ancient-looking!