There are so many easy invasive methods. For non invasive methods i Would suggest you to use any electrical or piezoelectric sensors.

There is two procedures:

1- If you have the velocity distribution , you can transfer it to pressure distribution.

2- Insert L shaped petote tube and link it to a pressure gauge or a manometer based on expected pressure range.

I hope this methods to be help full.

Best regards.

Alaa

Thank you.