I’ve seen some w463 with red seat belts. I was wanting to add red seat belts and later on do a few other red touches throughout the interior.

any source or lead on where to get them ?

 

Check this website https://www.safetyrestore.com/conten...red-seat-belts . I've seen a few youtubers take their cars there. They are located in MA.
The only catch is you live far you have to remove your seat belts yourself and mail it to them. The turn around time is 2 days I believe.

 

Direct from your dealer and have them install them there....