Are you setting a cache for use days/weeks later, or is this for use by you on a backpacking trip?
What part(s) of the Canyon will you be visiting?

The Ratsack guy in Flag seems to have 'flaked' and is not shipping, or responding to inquiries about, his product.

Cheap, effective alternatives include cookie tins (available in round, square, rectangular, etc.) or a (virgin) paint can.

kurt