I've got all four South Arabia coins exactly that way. Through a proof set.
North Yemen is also easy to get. 6 denominations, all of which you can get through 1980 proof set, which is quite common.
South Yemen would also be easy (through CSAN) if not for 1971 5 fils, which is very scarce in UNC.
Official (not Houthi made) made issues of modern Yemen are also easy to get. 5 different types. Usually sold as one lot.
Zaire - 6 denominations. With a bit of luck you can find a lot containing all of them
Somaliland - 6 types, usually solf as one lot
Namibia is also quite easy to get. 1993 set (or just a lot of those coins, if you don't care about sets. They are common)+2025 series, which is very common
Kiribati - 9 types. You can get 7 of them through 1979 proof set. The remaining 2 (magnetic 1 and 5 cents are relatively common)