The Johnes translations of Froissart and Monstrelet are available in digital form at Google books. Johnes did the only complete translation in modern English of either. His translations are stilted and less than entirely dependable, but they’re what we have if you want an unabridged modern version.
If you can read French, you can go to Gallica.
Extracts from Lord Berners’ Tudor translation are available here, including the Battle of Otterburn
Robert White’s History of the Battle of Otterburn contains extracts from contemporary chronicles of the battle.
There is also an extract from Fordun’s account of the battle here.