Unfortunately, we are in tough times and may not be able to get the exact speaker but it is the standard 50mm size. In the past I was using these but they are now out of stock https://www.digikey.com/en/pro...50-WP-16-OHM/9842378
I think you can make 2 of these work if you carefully cut the mounting tabs off (using metal shears- using a dremel around the magnet would create metal fuzz) Gikfun 2" 4Ohm 3W Full Range Audio Speaker Stereo Woofer Loudspeaker for Arduino (Pack of 2pcs) EK1725
Again, put these in series and that would be 8 Ohms.