!st question:
Are you just wanting to replace the coil?
(ie. you already have a good ignitor and rest of system)
If this is true, then I believe a coil from one of the newer (post 1980's) Mitsubishi Magna can be used, as it's for that same type of electronic ignition. Note: This will be slightly smaller that the bracket that held the other one in place.
Point 2:
I am writing this only as a guide, please find out more before you act on this.
I have done a set up of 18RG electronic dizzy using 22R internals with coil and ignitor from (I think) a 21R or 22R.
Does the 2TG normally have an internal ignitor (I have been in contact with someone who has run an internal ignitor with 2TG internals)
Go to Repco or Supercheap or somewhere like that and ask them a few questions about the compatibility of a coil from another car with similar electronic ignition.
Sorry if all I did here was confuse you, but I don't have any experience with 2TG's, only 18RG's.