Common "flutter" choices with link to manufacturers site below. Aerobika seems to be the most preferred/commonly one used. Probably because NJH started recommending it a few years ago.

It's really personal preference, trial and error. Until recently, I used aerobika during 7% saline neb. Now I don't use a flutter device at all. I neb hypertonic saline directly into lungs per Dr. McShane's recent talk. I do not miss the flutter and it's one less item to clean/sterilize. Fortunately, I can get the gunk out through autogenic drainage and ACB (active cycle of breathing.)

PARI O-Pep
https://www.pari.com/us/products/airway-clearance-devices/pari-o-pep-us/
Acapella Choice
https://www.icumed.com/products/airway-management/respiratory/bronchial-hygiene/acapella/
Aerobika
https://www.monaghanmed.com/product/aerobika-opep-device/