The oil feed to the gear is usually via one of the frame clamps/brackets which hold the gear in the frame. I thought that on the 1923 model there was an oil pipe which ran parallel to the pipe which fed the plunger under the tank and which was simply operated by opening and closing the tap occasionally to permit the oil to flow (see the picture below from an example sold at Bonhams recently). I have this system on my 1925 Super Squirrel. However the Book of the Scott 1921 refers to a plunger which it suggests is operated every 20 -30 miles.
Anyhow, if you are to dispense with the feed/plunger all you really need is a separate tank and an oil pipe from that tank to the oil feed in the bracket with a conveniently- located tap.
I have found the oil tank in the second picture which might be of use to you – it is surplus to my needs. Let me know if you need it.