https://www.tpaktopc.net/d2strcltch.htm
I think the General gear choice is a good way to go but was hoping to find a serviceable early disk.
There was a Company called Miba that was providing the early style but they are not responding to their contact e-mail.
If you have your worn out disc, just get it relined. Try Capital Clutch and Brake, 916-371-5970. I was planning on having them do my disc for my 22, and they said $65 to $115 depending on size. I did not need it done after inspection, but I think that will be much cheaper than new. Good Luck.
Finding a NOS clutch disc for the D2 J model may be quite difficult, last time I saw any available was more than 20 years back, and those were the last remaining old stock that I could find, I don't think Miba has made them since the 1990s.
I think the best option is, you can use the complete clutch assembly from the U model, the clutch disc is still available for that.
Is the 3J disk relinable? I'm looking at the picture on GG's website and I'm looking at the plate in my 3J and it's just cut out of a piece - nothing to reline - https://www.steeringclutch.com/images/CLUTCH%20DISCS/CAT%20D2%20FLYWHEEL%20CLUTCH%20DISC.JPG
The disk is a solid piece of highly compressed fiber formed to fit and ride between two metal disks.
Miba still shows that they make the disk but they have not yet responded to my contacts.
Miba friction group USA, 1 586 939 0620
Miba sinter group USA, 1 740 962 4242
Give them a call, should get some information, let us know.