Bars in Roman numerals

[topological-modular-forms]

Adrik Ivanov mentioned bars in Roman numerals, as in e.g. Alegreya:

Some Roman numerals are encoded in Unicode, but this seems likely not a definitive solution, so I should figure out what would be the best way to implement the option to have bars in the Roman numerals.

the_guruji mentions:

looks like alegreya does this having stylistic sets. iirc a few other huerta tipografica fonts do this as well. just checked andada and piazzolla and both have this.