In case someone searches on this thread here is what I have found.
I have read the latest regulations I could find and as far as I can see the law says the lock/hinges/fastenings should be "...PREFERABLY made of copper or brass...". It does not say that it NEEDS to be. By the same token, it does not say that wood or copper is necessary for the box either, it says "...or other suitable material". My reasoning then says that for example a plastic lockable container with the word Explosives written on the side would work in the eyes of the law. It has no metal parts whatsoever (although thats not a requirement), is portable, and will even melt to not allow dangerous pressure buildup in the case of a fire (not a requirement again, but a good thing).
Here it the actual act with relevant sections cut and pasted:
From the Act Justice Department. (EDITED) Current as of 4 Feb 2009
EXPLOSIVES ACT
Class 1 — Gunpowder Class
35. Any person may, in respect of safety cartridges, load at a place other than a licensed factory if
(a) the loaded safety cartridges are not for sale or for any commercial, industrial or business use;
(b) the explosive used to load the cartridges is kept or stored in accordance with the provisions of Part XIII;
(c) not more than two kilograms of explosives, other than safety cartridges, are kept in the place;
(d) the artificial light, if any, used to illuminate the place is of such construction and character and located in such a manner as to not cause any danger of a fire or an explosion;
(e) no fire is kept in the place;
(f) no person smokes in any part of the place;
(g) no person has in his possession a match or other fire producing device in any part of the place; and
(h) no work or other activity, other than the loading of safety cartridges, is carried out in the place during the period such loading is being carried out
In this Part, “suitable receptacle” means a substantial box or substantial container,
(a) that may be placed inside a building that is not itself adapted for the keeping of explosives;
(b) the location of which is not changed from that prescribed by an inspector or under provincial or municipal law;
(c) that is kept away from goods of an inflammable nature; and
(d) that is of easy access for removal in case of fire.
137. In regard to any receptacle, the following provisions shall be observed:
(a) it shall be provided with a closely fitting lid secured by a lock, and hinges and fastenings, preferably of copper or brass, and otherwise closed and secured so as to prevent unauthorized persons having access thereto, and shall be kept locked except when required to be open for receipt or removal of explosives, or other necessary purpose;
(b) it shall be exclusively used for the keeping of explosives;
(c) it shall be made of wood, copper or other suitable material;
(d) the interior of the receptacle and all fittings therein shall be so constructed, covered or lined as to prevent the exposure of any iron or steel, or of any hard or gritty surface, or the entry, detaching, or accumulating of grit, iron, steel or similar substance;
(e) the interior of the receptacle shall be kept scrupulously clean; and
(f) the receptacle shall have the word “EXPLOSIVES” conspicuously displayed thereon on a contrasting background
