In Canada, it is somewhat rare to find a legislature with only two parties represented.
At the moment, four provinces (BC, SK, PE, NB) qualify. In the US however, it is rare for anyone except a Democrat or a Republican to get elected. Independents do win. Joe Lieberman, for example. Technically, he leads his own statewide party that nominates only him, but in reality of course, he is an Independent. I decided to take a quick look to find third party elected politicians in the US.
First, former members. A Green was elected to the state house in Maine and a member of the Constitution Party in Montana. Neither members currently hold seats. A Green was elected in Arkansas, but defected to the Democrats.
There are only two states with current real third party members that have been elected to the legislature. In New York, the state assembly has four parties. Along with the D's and the R's, there is a member of the "Working Families" party. The party is generally moderately left wing. There are also members of New York's "Independence Party", which descended from the 1992 presidential bid of Ross Perot. The party is right wing. One member was elected from this party and another has defected from the Republicans. The member for the WFP is from Long Island and the original member from the IP is from up state.
The only other state with third party members is Vermont. There, a strong "Progressive Party" has won seats for the past number of years. They currently have one State Senator, from Burlington, the state capital. In the state house, there are 5 members from the Progressive Party, from all over the state. Although Bernie Sanders has never returned the affection, the Progressives have been his biggest supporters. Sanders, currently, is a United States Senator from Vermont and officially sits as an Independent. The Progressives could be considered NDP-like in terms of policy.
Sorry, no extra data today!