Map packs 3 and 4 are still available for purchase here:
http://www.miniaturemarket.com/collectible-miniatures/star-wars-miniatures/star-wars-maps.htmlOne map from Map Pack 2 is also there (Abandoned Casino/Ugnaught Mines).
3 of the 4 more recent releases are also there. The new Cantina Map is not there, but it's the most recent so you can probably find it somewhere. There is a brand new map not yet released that is still on Kickstarter - it includes Anchorhead from Map Pack 2.
So the only ones that are hard to find are Map Pack 1 (5 of the 6 maps - Theed Palace from that pack was re-printed with Smugglers Base and is available at the above link); and Map Pack 2 (5 of the 8 maps. Abandoned Casino/Ugnaught Mines is still available, and Anchorhead is being reprinted.) Oh - and the ultra-rare Sith Temple that was never released for retail sale.