They're no
that obscure.
Here are some Regina Sport machines I've found earlier, while researching my find:
Art F’s Regina Sport on OTSG
Emile's Velosvintage blog
Rafbor's Regina Sport ‘3 Tubes’ on Tontonvelo
Vincent's white SS
Several Reginas in
this Tontonvelo thread (Giovanni's light blue Regina, Le Voyageur's grey example, and another blue one owned by Marco47)