My replacement amplifier arrived today!
It's a Pyle PLMRMP1B, a tiny little marine amplifier. Claims to make 2x 100watts RMS, but it's more like 2x 20watts! Still sufficient for my speakers and the MX-5 though. And I'm happy with it's sound quality, not the best amp I've heard but for the size and money it's good.
The amplifier uses a STA540SAN made by STMicroelectronics. Specs confirm the power to be around 2x 20watts RMS.
I installed connectors on the little amplifier, and it also comes with a remote volume control knob. Will have to find a place to install/hide it.
Everything mounted up.