Roland Alphajunos are overlooked today because of their lack of slider and knobs and their controller PG300 is hard to find and not cheap.
The Behringer BCR2000 is the easy way out, the perfect substitute to the PG300, take a look at this video…

The Behringer is a midi controller that can send even sysex messages, the old Roland Alphas work  only with sysex messages so you have to map the BCR2000 with the learn function and a virtual pg300 programmer.