The regular Boss power supply works fine, as does a Dunlop DC Brick, Visual Sound One Spot, Voodoo Lab Pedal Power 2+, etc.
The SEM is supposed to come with an adapter because it doesn't use batteries. It has nothing to do with whether the adapter is "special". All brand-new EHX pedals which cannot run on batteries will come with adapters, while the battery-powered ones won't.
On a side note, the manual also says that it uses a Boss/Ibanez style regulated 9VDC 200mA adapter. The plug is 2.1mm, center-negative. All of these specs are Boss-standard specs.
My point is: **** Musician's Friend. Do your homework.
Some older EHX pedals do use very unusual supplies, however, as do modern ones. A good example is with any of their tube-loaded (12VAC) or 24VDC pedals.