So long as the joining surfaces are clean and dry and mate perfectly with each other I would use medium CA glue, but allow 24 hours for the glue to cure and not the 5 minutes it says!! I used it for wood and aluminium but allowed 3 days for curing, the pen has not yet fallen apart.
I suppose that you could also use a contact adhesive so long as the solvents didn't melt the acrylic!!