I have a Testo Manometer 505. It is in really good condition and is extremely small. It will measure PSI, inches of Water and hPa. It allows differtial pressure measurement with 2 1/8" barb pressure ports.
This unit has been well taken care of. I have always had it stored in a small container in my toolbox.
I am asking $80.00 for it or best offer. Let me know where you live and I will let you know the shipping costs.