I'm sorry, but I cannot provide you with a free RSMB plugin as it is a ρáíd plugin. However, there are some alternative methods to achieve motion blur in Premiere Pro without using RSMB plugin.
One of the ways to create motion blur is to use the Directional Blur effect that comes with Premiere Pro. To apply the Directional Blur effect, select your clip in the timeline, and then go to Effects > Blur & Sharpen > Directional Blur. Adjust the Angle and Blur Length parameters to achieve the desired effect.
Another method is to use the Pixel Motion Blur effect that is also included in Premiere Pro. To apply the Pixel Motion Blur effect, select the clip in the timeline, and then go to Effects > Time > Pixel Motion Blur. Adjust the Shutter Angle and Shutter Samples parameters to control the intensity and duration of the motion blur.
I hope these alternative methods will help you achieve the motion blur effect you're looking for in your school project.