best advice is to look under plastic in the yellow pages.
http://www.yellowpages.ca/search/si/1/plastics/manitoba
heres a couple
Laird Plastics
8 Plymouth Street, Winnipeg, MB R2X 2V7
Telephone : 204-632-1136
Acryl Design Ltd
740 Century Street, Winnipeg, MB R3H 0M1
Telephone : 204-783-6064 Free Call
if you look at the link i posted, i'm sure you'll find something closer to you, good luck.