SDC Pro 2 ... or SDC HD?

Not sure that you'll find a proper service manual for these (or any other Stryker product, for that matter) - more like a "Troubleshooting" section in an operators' manual (if you're lucky).

Meanwhile, I would be interested to hear how you get on sourcing the SMPS. Is
Hamiltone on your list, I wonder? And lastly, what's wrong (the fault) with your SMPS - a dry cap (or a "blackened" component - due to a failed cap) somewhere?
Either way, a nice little fault finding exercise for your apprentice. I recommend an ESR Meter, if you don't already have one - and suggest you start with the output electrolytics!
Note the "10 year warranty"!