Welcome to the forum @maketolearn. The Sangaboard can be replaced with an Arduino nano and the motor drivers that usually come with the little stepper motors. This is detailed as the electronics workaround. The functionality is identical to the integrated Sangaboard v0.3, the wiring is just a bit more messy. The nano converter plate in that link will only work for a Raspberry Pi 4, not a Pi 3.
@filip.ayazi has developed a prototype Sangaboard v0.5. There is a separate thread here about that with some details of how to get one, although it may not ship to your area. Sangaboard v0.5 now available - OpenFlexure Forum.