Sort of surprising that a version of this didn't exist. You can get N95 fittings, since there are different sizes of N95 available, and though it's a bit if a process it's not hard to see how a less rigorous version could be developed to test the fit for other masks where there's not that tight seal. The process involves wearing an N95 that has a small valve to accomodate a rubber hose, and they have you do different things to assess the fit (taking deep breaths, moving your head and neck around to see if movement effects the seal, reading sentences aloud).