The main pressure sensing film appears to be Fujifilm Prescale. The range of pressures listed above falls directly between two different film ranges. The ranges for different diameters are listed below. For a fairly small diameter the Super Low pressure type is appropriate.
For a Fujifilm Prescale film with Low pressure rating, the acceptable range of pressures ranges from 350 to 1400 psi. Translating this to force assuming a 1" diameter circle of contact area, this comes out to a force range of 274 to 1000 lbs.
The table below assumes 500 lbs force
Diameter | Film Type |
d < 1.35 | Low Pressure |
1.35 < d < 3 | Super Low Pressure |
3 < d < 4.768 | Ultra Low Pressure |
d > 4.768 | Extreme Low Pressure |
Specifications links
http://www.sensorprod.com/prescale/product-pages/prescale/prescale-pricing.pdf
http://www.bestech.com.au/wp-content/uploads/brochures/PRESCALE-Product-Guide.pdf
An Amazon link is listed below
https://www.amazon.com/dp/B079C6JR63/ref=cm_sw_r_cp_ep_dp_yTxTBbW2AA2PA