Hi Cerulean,
A lot has said above, so I limit to numismatics...
Regarding Egypt, if on a business trip, you'll end up in one of the hotels on the Corniche or even better the Marriott in Zamalek (island in Nile). Most of them have (hassle-free) souvenir shops selling recent coin sets in EF quality and some (namely in Marriott) they do sell 1-5-10 commemoratives, as well.
There is also a shop of the Central Bank at the airport, although opening times are very hectic, they sell a lot of the commemoratives at reasonably prices.
In Khan-Al-Khalili (the historic Souq (market)) there are various shops who sells coins, besides Egyptian, you can pick up nice trading dollars, if you are confident to distinguish the original from the majority of fakes. Patience there brings results, though!
Coins or anything you buy in the Souq, bargain confidently! The first question you'll be asked: "What-country?"
your answer will determine the price!... If your answer is "American" calculate a 400-500% mark-up (source: Souq sellers from Khan-Al-Khalili

) SO, if the quoted price is 500, aim at getting it for 100, so start the game at around 60, moving in smaller steps than the seller.
Ask for the price ONLY, if you really want to have the thing! - Your last weapon to achieve the best price is to slowly walk away ... chance is there, they will walk after you to complete the deal.
The other winning strategy is bargaining for something, and having another item in mind (of lower value of course) to ask as a gift at the very end of game.
It is difficult to find good quality coins in circulation.
Contrary to one of the above post, I have never experienced problems bringing coins out of Egypt, for other antiques, it might be true, though.