Changing font in CollectionView UIIndexBarAccessoryView

I have a 600 item Collection view for which I implemented a quick access section Index.

The implementation uses the usual: indexTitles(for collectionView) and CollectionView(indexPathForIndexTitle: title: at:)

All is well, except that the collection titles are in a foreign language (latinized Coptic) and 3 of the 25 title glyphs are not in the SystemFont, so the index is drawn with these titles as question marks in boxes. The problem glyphs are "Ꜣ"(unicode A722), "꟣"(A7E3), and "Ꜥ"(A725)

I drilled down on the subviews of the CollectionView and found I could access the index using:

let subviews = myCollectionView.subviews
if let indexView = subviews.first(where: {String(describing: type(of: $0))=="UIIndexBarAccessoryView"}) {
     print(indexView)
}

Examining the contents of this UIIndexBarAccessoryView (which seems to be Private), it contains a _visualStyle property object which holds a _font.

How can I "legally" change the font for the indexBarAccessory to one that has the required glyphs? The rest of the App requires the local language to be English(US)