Nice project, you are going a lot further than I have on my various Boxster engine interventions.
I went back and looked at the site that I bought my oil pressure gauge from and you were right I was on the US site. Prices have doubled in the last three years.
Here is the link to the Canadian site for the heritage gauge that should work with the 996 sender and it is currently relatively cheap.
https://www.cip1.ca/vdo-a2c53402717-s/