Northman
What has worked well for me is to joining a group in my solo canoe.  I will be self sufficient so if things do not work out I can go my own way.   I have always been lucky and gotten people I get along with well.
When deciding if a person will be a good partner for a trip ask some questions about what kind of trips they prefer and see if that matches with what you would like to do.  When asking how far you travel in one day do not settle for some thing like “we go hard on the days we travel”.  Ask how many miles and how many portages so you do in a day or ask for the lakes they camp on for a recent trip and judge for your self if you would want to do that trip. 
Jimbo’s suggestion for Copia is a good one if you do not meet any one you will have a good time anyway.