In the Edmonton chapter of FVC, we have been talking about the policies and resolutions adopted by each party RE proportional representation. Some parties have gotten quite close, the Alberta Party resolution on adopting PR got defeated by only two votes. Given that they got crushed despite increasing their vote share in April, that probably will make many members rethink.
The PEI PC Association holds AGMs in November, and monthly party councils where all members of the party in attendance are members. If some people in favour of PR who are centre right can either be persuaded or already are, they should be able to get a resolution supporting it. Remember, Angela Merkel, a longserving centre right politician, got elected and has maintained her power longer than almost any other Prime Minister in Canada, and has maintained CDU/CSU influence in the government for a long time, and in the German second chamber as well, the Bundestrat, the party has consistently sent delegations large enough to give it a strong voice in any measure or vote. This despite Germany using MMP and same with each state and municipality.
The NDP federal party has a policy already to support PR and make it a condition of supporting any minority government or coalition. A few parties like the Alberta Liberals, Greens, and Communist Parties also have resolutions of support for this.
Try convincing these party members and conventions/AGMs to pass a resolution that is binding on the leadership. It is less flashy than a leadership election or a general election, but they are important and affect the real policies that parties partake in. It also drives up the discussion on PR during a general election. We already have Sean Graham, the author of Dual Member Proportional, in the NDP standing Council of Alberta who spoke at our local chapter meeting in March. See who else you might be able to recruit.