Anyohaseo, James!
Where you will have to go depends upon the season, as many floatplanes in Canada will be shut down from October to April or May. There is no such thing in Canada as a MES rating - you get your Multi rating, and then you get your seaplane rating, and it is automatically considered to include multi/sea.
A good place for a seaplane rating is Ocean Air
Floatplane Training / Seaplane Training - Float Plane Charters -Seaplane Charters - Victoria, BC, Canada - Ocean Air Floatplanes, in Victoria, BC. Dave has lots of training and operational float time, and will set you up in a C-180.
I'm not sure that I know of any multi/seaplanes for rent or training. You might try Randy Hanna at Seaplane academy in Nanaimo, BC +1-250-616-5885 as he used to run a twin of some sort on floats.
I know nothing about Licence conversion, sorry!
Good luck!