Stonegrind might be tricky as the machine must have wide stones for snowboards.
You may call places that sell snowboards, but be aware some shops outsource the service.
Sport check - belt sanders only, low pricing
Sports rent -
Abominable -
University of Calgary-
SKiWest, TechnoSport, Felix - all do skis, no idea if they do snowboards.
Check kijiji as well - be aware most adds are for manual maintenance - no machines;
The turnaround time is something to consider as well.
Your best bet is to have your gear DIY maintained, after the initial shop tune.