Dear Sir
Without any external source of energy (solar etc.), any existing battery applicable for your device will be discharged by self-discharge in 2-3 years.
Also, GSM device consumes a lot of energy.
The real device I'm made has a 6-8 month of continuous work with GSM communication 2 times per day. Most large existing battery was used and communication was really short (one value of measured weight transmitted). And a lot of efforts was applied to minimize a power consumption between seances.
However, I can make such device for you if you are ready to discuss more real battery lifetime.
With best regards
Maxim Bulkowsky