I used to have an NOS EGR Rev Sensor, but I'm not sure if I've sold it. Picture of it is below.
Revolution Sensor, 25068-S8200,
US$50 + shipping
I have seen two bad ones, so I know that they do go bad.
Because you have to remove the IP sprocket (and all that entails) to access the Rev Sensor, it's a PITA to do, or even to get from a JY or donor engine.
If I still have this one, I'm willing to part with it. If it's prepaid (via PayPal, etc.), I'll ship it to Malaysia.