Forced Camera Upgrade Has Made My Accessories Useless

I bought a HERO 8 a few months ago that turned out to be defective. Support agreed to replace it, but due to stock levels and discontinuation I was told I would have to be shipped a HERO 9 instead (yay, upgrade!).

Problem is, I do multi-day, endurance shoots so had already invested heavily in multiple sets of batteries and chargers for the 8. They are incompatible with the 9, which means I had to invest over £100 for a second time to stock up on batteries and charging equipment.

Since my first set of batteries are perfectly functional (I assume - most are unused) they aren't covered by the returns policy, as confirmed by the Support staff member who offered the replacement. Even if I sell them on they will have lost a lot of value being second hand. This upgrade has screwed me over a bit.

Mainly just wanted to vent, but if anyone knows of a good replacement scheme or a clause in the returns policy that I've missed, please let me know!