Flow Sensor Recommendation Needed

Flow meter recommendation needed without breaking the bank. Meter will be used for indication only.

Service: cooling water return
Temperature: 500 deg. F
Pressure: 800 psig
Flow min/norm/max: 1M/ 1.5M/ 2M Lb/hr
SG: 1

Some side note: pipe is not always full

Any recommendation will be highly appreciated!
Check out Panametrics (GE?) transit time clamp-on ultrasonic flow meter. I believe they have transducers rated for 500 Deg F.

Last time I checked, clamp-on assumes a full pipe; I don't think even multi-path can deal partially full pipe.