The 2N5210 is an NPN BJT with an hfe range of 250–900. With that wide of range, 2N5088, 2N5089, BC549C, and BC550C would be suitable substitutes. The MPSA18 gain range may be a bit too high. I'd either measure them or stick to the BC series since the 2N5089 is a higher gain variant of the 2N5088 and its max parameter exceeds that of the 2N5210. As always, confirm the pinouts before installing the device.
