Yes, you can buy spark plug wire, MSD boots and terminals, epoxy/glue, solder, heat shrink, etc. and do the work yourself. However, if you have any question about your skills and knowledge to do the work, then why?
The connections are critical to be perfect and sealed for saltwater riders especially the plug wire to spark plug terminal connection.
We have sold over 170 JSS coils to Xers with almost zero defects or issues over several years. Any problems are usually later found to be other electrical components.
JSS always stands behind their work.