have a look at G4CQM's coaxial dipole, does away with the requirement for  balun, maybe just add a Tonna ¼wave half loop on the feeder  https://qsl.net/g4cqm/wave_antennas/DIPOLES.html
also maybe look at GM3SEK's talk if you can find it (on rsgb or youtube ?) about baluns and ferrites