There are few similar models (link) that should be loud BUT there is a correlation from after a point, more loudness needs more money. In portable or not portable models.
Something like this pretty much is how loud you can go with the shape / type.
There are really really loud BT speakers but they do cost also. Low manufacturing amounts and low sales. Maybe something in the used market could also help with the loudest ones?
BoomBox types and similar ones is the next step. Bigger size, more volume.
Extreme option is BT PA-System / speaker. There are few in budget range but don’t know how loud, loud anyways but…
They usually need power cable connection but loudness is there. Really really loud is possible, for xxx of moneys. Going in the +120db range. Extreme option example.