If you are looking for Much Cheapness, then any PSU that outputs 15v and can do at least 2.4A is fine.
Then, as Matt says, it's down to what the plug type is.
It might be a standard one, or it might be proprietary.
Most normal barrel-type ones are + centre, which is correct for your thing ("positive pin").
Many cheap PSUs come with a selection of plugs which can be fitted to the end of the cable.
So if you don't know the exact type, then this may be an option.
You might need to compromise on the right-angle thing.
Much Cheapness comes at a cost.