Thanks, but I probably do not want to get into any customization.
A non-custom option with a 240mm lens on 4x5” might not be accurate at portrait distances, which is probably a part of why it isn’t easy to find.
You could consider something like a Graflex SLR or a Gowlandflex, if you want to be able to focus up to the instant when you release the shutter.
However, if you’re using a view camera on a tripod for portrait subjects, and the subjects can remain relatively still, you can use a string, which costs virtually nothing, and it’s dead accurate even at wide apertures and close distances. Tie a string to a fixed point on the tripod and put a knot at the end that will measure a fixed distance to the subject’s head. You don’t have to focus on the point where the knot touches the subject, but you should try to keep it consistent. Use the string to position the subject’s head at the focal distance, focus, and then periodically during the shoot, you can leave the focus there, have a filmholder in the camera with the darkslide drawn ready to shoot, and periodically use the string to check the distance and make sure the subject hasn’t left the focus zone.