Mulches from the garden centre are fine, but there are many different kinds out there. Cypress mulch is not available at all garden centres (Bradford Greenhouses generally carries it). Many sell cedar mulches that have been dyed different colours, and sometimes they are dyed to look like cypress. They may even have a label saying 'cypress' that refers to the colour, not the mulch! And of course, cedar is considered toxic to herps, though I know of people who've used it quite successfully with some reptiles.
Dollarama has become Jenny's favorite store! We get lots of great stuff there. We're also big fans of cardboard boxes, margarine tubs, etc. When we go to Costco, we take lots of extra small flat boxes, and occasionally one of their staff asks why we want so many- it starts some interesting conversations sometimes!