Here are the O-ring part numbers for each of the M200 gear and the flap actuators:
3 each AN6227B-17 (MS28775-212)
1 each AN6227B-10 (MS28775-112)
The flap and landing gear selector valve use the following seals
2 each MS2775-117
1 each 1161N52-204 [8-point seal 70 DURA Buna N from McMaster-Carr]. (They also have a reinforced high pressure double O-ring type seal, but it is a harder rubber and more difficult to install)
The AN/MS O-rings are available from Aircraft Spruce. I recommend ordering a few extra of each so you have spares in case one gets nicked or cut during installation.
The step actuator has a Beech aircraft brake cylinder part number. But I don’t recall the O-rings required for it. Access to it is best achieved by lifting the rear seat/cargo floor deck.
Hope this helps,
VR, Tom Thibodeau