So sorry to hear this mate but what a company! Have they been going long?
The Eastron meter is probably the SDM120 but, there are severa versions of it however, they are widely available if they shopped around. Send a pic and will confirm but, you shouldn’t be buying anything out of your own pocket.
Fogstar are a great company and glad they are looking after you, even though its not their problem. Not seen the new battery but, most likely an kW upgrade on original?
You should consider seeking compensation from the instaler.