Photo shot at Dunham's Reservoir, Grafton NY.
I forget where I bought the traditional oarstraps, but the plastic oarcages are from Concept2. I needed pins that fit the .5 inch diameter of the oarlock and the 13mm diameter of the concept2 cages. I made a drawing and had Bob from Springfield Fan Centerboard Co. make them (silicon bronze).
The pins have a threaded hole in each end. The top one takes a bolt and washer to hold the cage on, and on the bottom there is a threaded plastic knob (Tru-Value hardware) that holds the pin tight onto the oarlock and allows for a quick take-apart.
The concept2 cages are quite subtle. They let you adjust the pitch angle of the oar and how high off the gunnel the oars sit, which may be different right and left if you use a crossover grip.
I'm using a dacron cord instead of a button to orient the oar lengthwise -- and I've glued some wood strips on the oar to give it a slight D shape under the leathers.