Here's their web address, they have aircraft around the globe but the head office is in Calgary, Alberta, Canada.
http://www.borekair.com/
You could also try this company, they also have twin otters on skis. All northern Canada though.
http://www.airtindi.com/
I hope that they will be able to offer some helpfull advise for you.
Also, try this site
www.avcanada.ca there is bound to be someone on there that has flown skis.