Then there is another way with RAM mounts. Which I love.
Mount this to your eyelet. https://www.amazon.com/Mount-Motorcycle-Base-Hole-1-Inch/dp/B0012TRIY4/ref=sr_1_1_sspa?ie=UTF8&qid=1522884786&sr=8-1-spons&keywords=ram+mount+9mm&psc=1
Then use these to mount the camera.
RAM Mounts are the shyt. https://www.rammount.com
https://www.amazon.com/dp/B0012TRIY4/ref=cm_sw_r_sms_c_api_i_2JeXEb2D9BVHF
RAM Composite Double Socket Arm
And whatever phone mount. Works great!
Not sure what mount they use in NZ, but if you are looking to mount a smartphone to a foot-stretcher, look at the modular mounts used on motorcycles and bikes. Two challenges for rowing iphone mounts are: to be quite secure to avoid dropping the phone in the water and to enable adjustment to any angle to make the screen readable in a wide range of light intensities and directions. Here's what I found worked for my 1x (though there are more options now than 4 years ago when I ordered these parts).
You can attach this widget with a bolt to your foot-stretcher to provide a base for connector and phone holder:
https://www.amazon.com/gp/product/B0012TRIY4/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1
...then use this connector which rotates in all directions:
https://www.amazon.com/Mount-Double-Socket-1-Inch-RAM-B-201U/dp/B000UGZTQO?ref_=ast_sto_dp&th=1
...and this widget to hold your phone (also moves in all directions on a ball joint):
https://www.amazon.com/gp/product/B0055PH0XA/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1