I have a crazy Idea I was thinking about before, not seriously but it might just solve this issue, somewhat.
What if you designed an item catalogue, like those mail order catalogues you used to get. It would work similar to selector tag configuration or extruder molds, except it uses coins.
Basically the catalogue could be read and would include recipes for everything that could be bought. These recipes would consist of the catalogue being surrounded with the appropriate coins as payment. I know it sounds kind of dumb but you could resolve any missing items by creating a payment recipe for them and you could include coins of materials that are currently redundant. More realistically it would require a machine and time for the item to be ‘delivered’.
Alternatively you could give them a matter fabricator recipe but that would put them quite late-game, or have them appear in Gregtech Vaults but would make them difficult to aquire.