What have you done to me? I went off to eBay, just curious, and now I've ordered some!
The OP is in Spain, so....http://www.ebay.co.uk/sch/?_nkw=latching%20relay&rvr_id=280887506947&clk_rvr_id=280887506947
... from the UK should be attractive? GBP 1.25 + reasonable shipping. (GBP1.50 to UK address)
These have 5v coil, separate coils for "set" and "reset".
BUT! If you don't need the "latching" aspect, why not just ordinary relays? Should be cheaper.
Even if you do need latching... with the Arduino's "write to (built in) EEPROM" capability, you can have "preserve relay state across power cycle". Of course this option won't (always) do what a latching relay will: maintain the relay state DURING a power fail... but whatever it is controlling will be "mis-behaving" during the power fail, anyway, won't it?