Help Locating Wedge-tailed Eagles

I am trying to assemble a complete series of the Australian Wedge-tailed Silver Eagle in PCGS MS/PF 70 and have hit a wall. The 2016 is the latest, having all three finishes from 2014 through 2016. 2017 is missing the standard proof. Why are these tough to find beyond 2017? More importantly, where can one find these aside from EBAY where I've acquired them?
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There were a whole bunch of graded examples on Stacks this past Wednesday.
Keep an eye over there for their next online auction this Fall.
why not continue to buy on ebay?
I bought a silver 1 ounce year of horse 2014 . Piefort.
I give away money. I collect money.
I don’t love money . I do love the Lord God.
I bought all that was available. None between 2018 and 2019, at least in the past several months when I began the series. And I don't see that changing any time soon. Plenty in NGC holders though.