From fresh fish fish to cooking oil to betel nut, the Mani Sithu Market in downtown Nyaung-U is the main local market for the town. It's a permament market and set up under a light wooden structure that occupies a large block in the middle of town.
You won't find much in the way of souvenirs here--it's primarily a local morning market rather than tourist market.
Photos of Nyaung-U Market
If you fly into Bagan, you'll fly into the Nyaung-U Airport (also known as Bagan-Nyaung U / airport code NYU). The train to Bagan also terminates in Nyaung-U.
The Mani Sithu Market isn't far from the airport and is close to the impressive Golden Shwezigon Pagoda.
Travel Advice for Myanmar (Burma)
You can find the latest U.S. Department of State travel advisories and information for Myanmar (Burma) (such as entry visa requirements and vaccination requirements) here.
The British and Australian governments offer their own country-specific travel information. You can find the British Government's travel advice for Myanmar (Burma) here and the Australian Government's here.
Health & Vaccinations
The CDC makes country-specific recommendations for vaccinations and health for travelers. You can find their latest information for Myanmar (Burma) here.