Seeking Advice Re: 6 speed derailleur replacement

[ofcounsel]

My son's bike (Cannondale Trail 20) currently uses a Shimano Tourney TX35 6/7 speed indexed rear derailleur. His gearing is a 36T single chainring up front and a 14-28T six speed freewheel in the rear. His shifter is a 6 speed Shimano RevoShift.

Any suggestions for a lighter weight new or NOS rear derailleur to consider?

[ultraman6970]

Big chance that anything shimano up to 8 speed might work just fine. After 8 speed starts getting weird with the cable pull ratios.