maybe you have the sensor in hand already
do you know what is a "bourdon tube" ?
a tube wound into a spiral will try to unwind when subjected to internal pressure.
Thought experiment - take a long tube of rectangular cross section
and wind it into a spural.
Because it's circular in shape, the inside wall is now shorter than the outside wall so those two walls have unequal areas
width * 2 * pi * inside length < width *2 * pi * outside length
so the internal pressure makes unequal forces P X Area that try to straighten it out.
try winding a couple feet of your tube into a coil and blow in the end
if it moves perceptibly that's a start. you need to measure its displacement, maybe with a front surface mirror and laser pointer.
may not work at all. but it'll get your creative juices flowing.