Welcome to the forum.
Thanks, that's along the same lines as I'm thinking. The parts are readily available and I bought the longer screw (UK£12) which "looks" like it will fit, although I haven't got around to taking the casting off to check. I have a milling machine I can use to mill a slight flat where the adjuster screw comes out, so I'm hoping I will be able to fit a seal/washer at this point, something similar to the machines which do have the adjuster. I think my worst case scenario is that if it doesn't work, I just have to block the hole up again and all will be fine.I know of one person in Oz that modified an original TRA to incorporate above table adjustment not long after the MOF series came out with that feature. I believe his approach was to mode the lower casting of the TRA to accept the MOF screw and height adjustor system, and he may have also extended the screw to fit the TRA and come out through the lower casting. I know the mod was detailed in Woodworkforums.com at the time but suspect that all the pics from this thread would have been lost due to upgrades to the forum software over time, as we have lost a lot of the older pics. I seem to recall that the screw came though the lower casting at an awkward spot in terms of being able to create an effective dust seal.
I suspect that it should be possible to retro fit the screw and height winder assy from a current TRA into the older machines, but question the economics of the upgrade, the cost of parts could come close to the cost of a new machine if you replaced the lower casting rather than trying to drill your existing one to avoid the dust seal issue.
Please note that the above is based on my recollections from 12 to 15 years ago, and my Triton experience is limited to an original version TRA and a JOF, so no experience with a TRB, current version TRA, or MOF series.