Sorry I can't help with extra tube. I only have one and its in the grease gun
Have you tried googling a John Deere tractor? See if they would ship?
Try here:
http://www.greenpartstore.com/John-D...-AN102562.html
As far as putting in steering box, it's a piece of cake. Remove bolt, put end of grease gun hose in hole and pump till full.