Can you please direct me to a current product which replaces the boundry type omnidirectional SM91? I need approximately the same features.
The SM91 had a cardioid polar pattern. The replacement for it depends on your application.
If you are using the SM91 on a conference table, the replacement is the MX391 or MX393.
If you are using the SM91 for piano or kick drum, the replacement is the Beta 91A.