I want to grieve you, but in Prague there is no good sex shops where it is possible to buy DVD's. The big network Erotic City (http://www.eroticcity.cz/cz/prodejny.php) offer mostly Private and Hustler DVD's at very high prices (30+ euro). And maybe in this sexshop http://www.videocenter.cz/eshop.php?stranka=detail_pobocky&pobocka=5010 you can find something interesting (but i not sure about it).
Last time i visit local sex shops half year ago and hope what something changes in better way, but again not sure about it.

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