If you can substitute, then choose an Open Type font -provided you're on Quark 7 or later you'll easily insert special characters through the Glyphs palette.
If ever you're on a previous version, then I'm afraid you'll have to go the epyzee route detailed earlier. Unless you switch to a Central Europe font featuring the two glyphs into one.
Oh! maybe you can also switch the keyboard (the little flag in the top bar if you're on a Mac). Then you could probably type your text straight from it. To be tested. HTH.