If you are in need of paper maps, buy them in advance when you can. Amazon, Stanfords, the Map Shop and Omnimap have the biggest range online for English-speakers. Mapstor is best for digital maps. Maps sold in Central Asia are hard to find and will usually be in Cyrillic. An exception is Markus Hauser’s maps of Tajikistan, available at Geckomaps and PECTA offices in Khorog and Dushanbe.
The best place to buy maps in Central Asia used to be the cartographic institute in Bishkek (Kievskaya 107), selling Bishkek city maps, 1:100,000 trekking maps and 1:200,000 topographicals (200som to 370som). However, it has been reported closed – updates welcome.
Trekking Union TUK (Kievskaya 168) has a similar range of trekking maps for Kyrgyzstan. These usually have trekking routes marked out over the old Soviet maps, and so are still in Cyrillic script, although the first maps in English are now in production.
Realcom (183 Panfilov) also sells some 1:100 000 trekking maps (less choice than in Trekking Union of Kyrgyzstan) and some 1:200 000 topographic maps that aren’t available in TUK. They also have some GPS equipment.
Hiking maps are usually still the old Soviet maps, so you need to be able to read Cyrillic to use them. You can find many of them online for free. The JPEGs are best printed on 4 pages to get sufficient detail: I use the Rasterbator. Soviet Maps has background info and extra resources on the Soviet mapping project.
2GIS is a brilliant app (also available for the desktop) which has mapped Russian cities in extreme detail, and cities in Central Asia are coming online now. It shows you which companies are in each building, where to enter, finds GPS satellites very fast, and it works offline. Maps.me (works on Openstreetmap) is my go-to resource for general navigation if 2GIS is not available.