If changes of your data are not frequent, I suggest to use external serial I2C EEPROM for it is cheap and requires no backup supply voltage. All you have to do is to write (or get from some websites) the software to write and read the device. You need only 2 connection lines. Take 24C02 that is a very low cost device with 256 bytes of eeprom. Some of them can be written up to 10.000.000 times.