Following are a number of back-translations as well as a sample translation for translators of Isaiah 49:20:

• Kupsabiny: “The children who were born
  in the land of slavery shall say,
  ‘Here is very cramped,
  add to us a place where we can live.’” (Source: Kupsabiny Back Translation)
• Newari: “Your children who were born during exile
  will say in your hearing,
  ‘This place is too small for us.
  Please give us more space here to live in.’” (Source: Newari Back Translation)
• Hiligaynon: “Your (sing.) people who have-been-born in the times of your (sing.) mourning will-say to you (sing.), ‘This place is too small for us (excl.). We (excl.) need a bigger place.’” (Source: Hiligaynon Back Translation)
• English: “The children who were born while you were exiled/in Babylonia will return to Jerusalem and say,
  ‘This city is too small for us;
  We need more space to live in!’” (Source: Translation for Translators)