There are many previous posts here that cover building, Like I mentioned before, I would source a Toroidal Transformer, you can get them on ebay or Plitron make/sell them in Canada.
The Amplifier you have in that unit is rated at 10amps, so I would allow for maximum, and the fact that it is PWM unit you can aim for the maximum DC voltage allowed by the drive, because mean current can be controlled.
so I would aim for 70vdc.
This would require a transformer with 120 and/or 240 primary, with 50v ac secondary, I would go with a 600~750va. In all probability you are not going to be drawing max power for any extended period with one servo.
If you can only get a transformer with slightly higher secondary, it is an easy matter to take a couple of turns off. (approx 2 turns/volt).
Also, if you need a small auxiliary supply, it is easy to wind one on.
That is the transformer.
You will need a bridge rectifier, 200vdc 25~50amp, they are not much difference in cost as rating goes up.
You will need an electrolytic capacitor rated at 150vdc 8500µfd for 5% ripple at 10 amps.
Like I mentioned there are losts of previous posts here and if you google for DC power supply construction, you should find everything you need, if not come back with more questions.
Canadian Suppliers are Electrosonic, DigiKey, Newark and Active.
Al.