SnoMan said it best in the previous thread on this.
Airport currency exchange kiosk's are a good way to find current issue Unc notes.
I would like to add my experiences to this.
1) ARRIVAL currency kiosk's want to sell you currency for the country you are arriving in.
2) DEPARTURE currency kiosk's have a much greater selection of foreign currency.
3) Inform the vendor of your interest and intent; "I am a collector and am interested in purchasing foreign currency".
4) Inform the vendor that this may take some time and you do not want to impede other travellers who may need to make purchases more expeditiously than you. I have never had a problem with them setting my selections aside for me while I wait for other customers to finish their business.
5) You must have the time to peruse their inventory. (I have nearly missed several flights because I spent too much time buying!)
6) An alphabetical list of the countries you are looking for will greatly help with 4 & 5 above. Research what you are looking for!
7) It is difficult to see the condition of the notes being presented to you because the vendor is not allowed to give you the notes they are offering. Making a judgement on the condition of the notes that the vendor is holding up behind plexiglass can be difficult, it helps if they are sequential but if you are looking for radars etc. it can be tedious for you and the vendor. I often have to educate the vendor about the handling of the notes.
I have never paid more than 1 transaction fee regardless of how many countries were represented in the transaction. The more you buy the less the cost per note.
9) November 2013. Saskatoon airport announced that they are adding a currency exchange kiosk. Also in the announcement it was stated that you could pre-order foreign currency to be picked up at the kiosk in the airport. I doubt that you can specify the condition of the notes pre-ordered but if you can buy foreign currency at a kiosk in Saskatoon you can probably buy it at almost any airport.