Hello Hudson Bay,
Contact Tom at Orillia Aviation:
http://www.orilliaaviation.com/about.htm
If they are not training this summer, he should know who is. I know an instructor who trains floats there on occasion, I can ask her if she's working this summer.
I certainly encourage your desire for more training, but do your homework on what to expect. With a fresh float rating, you have a license to learn, you won't be let loose to explore the north!
I'll enquire of a float flying buddy who lives in Haliburton. I don't think that there is flight training there, as the lakes are a bit tight, with healthy hills around. Orillia is an hour drive away, and an ideal environment.
I live fairly close to the area you'll be visiting, If you need more help, let me know.
Cheers, Pilot DAR