The AK-47 is one of several rifles that (unmodified) fire a 7.62 by 39 (metric designation) round. The casings are readily available commercially and can be picked up off the ground at most rifle ranges. Some of the surplus shells are steel with brass coatings. Suggest you move to the all brass version to avoid future rust -- I see red ones on the ground at the range here.
The bullets are nominally .308 to .312 depending on the source and tolerances of the barrel. This is a short case compared to the 308 or 30-06 but the same processes for pen making can be followed allowing for the difference in length.
If you only need a few the vendors such as Eric Rasmussen are a good source as it avoids a learning curve and the associated less than perfect successes on working out the processes.
If you want a few cases to work with drop me a PM, but I will be traveling for the next week and will not get anything in the mail for 10 days or so.
Here is what I can make from some ammunition I have. As I said in my pm, if you want traditional brass, I'll have to order components.
This sample kit uses a 7.62x39 lacquered steel case, .310 bullet, mini-refill, long brass tube (because the cartridge is short), and black chrome (a.k.a. "gunmetal") clip and finial.
Visit any local gun range and ask for spent cartridges. Bet they can supply you a couple for next to nothing. You surely must have a local gun club you could approach.
All I have to do around my place is ask my neighbors ... we are all armed to the teeth and then some. Bet you have some neighbors that could help you or know someone nearby that could.