My favorite SD shield is from ADAFRUIT that combines a SD socket with level shifters as well as the well supported 1307 RTC with battery backup socket. A good value for two features that are often used together.http://www.adafruit.com/products/1141
Are you sure that this is compatible with Mega also? There is no mention about ICSP header, and in place of PCB where it should be is drilled array.... Also they dont show bottom of shield.
BTW i dont think that DS1307 is good solutin. Personally use only DS3231 module because DS1307 had big problems in long term accuracy.
You can try ask seller if they will ship in your country with extra cash. Or look for other sellers, but hope you will find a good supplier, as I mention - only few shields/modules with level shifters are on market for reasonable price....
Also look at this shield:http://www.ebay.com/itm/TFT-SD-Shield-for-Arduino-MEGA-2560-LCD-Module-SD-level-translation-2-8-3-2-DUE-/121161179201?
It also has level shifter. But it more proposed for usage with color tft modules (has STM32 compatible connectors). Thats why it is not so cheap, but shtill costs less than Adafruit
While searching for some components for my project, found this seller which ships worldwide - hope you are not from Hong Kong or China (these are exceptions):http://www.ebay.com/itm/Arduino-SD-TF-card-expansion-board-Shield-module-Stackable-module-building-block-/310735773715?