https://www.sterndrive.cc/Johnson-Evinrude-Complete-Lower-Units.html
Call them direct with your need. Have the year & model number of the engine handy when you call.
As Chinook said , it's probably the shift shaft seal or upper driveshaft seal but a pressure test will tell for sure. It could be the lower driveshaft seal under the pump but that would normally show itself in the water intake or out the prop area with the drive down. If the upper input yoke seal was leaking you would only see it in the bellows as said above.