I have a general explosives permit, which basically states that I can legally handle and transport high explosives in canada.
This things pretty cheap, it's just a piece of laminated paper with my name on it, DOB, height, weight, eye color, expiration date and a nice little police logo. The photo on the back is a simple passport photo I got at the local pharmacy, they cut the picture and glued it. Pic cost me about ~$10, the rest I could print out on my crap ancient printer.
I've used this at liquor stores, grocery stores, and even once at the airport... No one ever gave me shit about it. I got a driver's license and i'm 21(legal age in CA: 18), so don't really need to use it though.
You can probably find something easier to forge than a drivers license wherever you are located.
Or do what I did when I was 16: hang out in front of stores smoking weed and wait for someone who looks like he'd buy it for you, give him a beer or a few smokes for his trouble.