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There isn't one.
Despite generations of raising community funds and scraping together the necessary support to send previous Squads, RugbyWA has not seen fit to send a WA presence to the 50th Anniversary Tournament.
There is a NSWJRU hosted Barbarians XV which you would assume WA could have nominated players for and could've at least allowed some presence, but looking at the story linked below and, despite Northern Territory, South Australia and Tasmania managing a player to that team, to my knowledge, none are from WA.
I hear some talk of not meeting RWA's "strategy".
If that is the case, I would suggest the rest of Australia have a different strategy, as literally every other catchment has a presence.
https://schoolsrugby.com.au/boys-xvs-team-lists/