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 is the cartographic institute in Bishkek (Kievskaya 107), which sells Bishkek city maps, 1:100,000 trekking maps and 1:200,000 topographicals (200som to 370som). Trekking Union TUK (Kievskaya 168) has a similar range of trekking maps for Kyrgyzstan. These have trekking routes marked out over the old Soviet maps, and so are still in Cyrillic script.
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.