I don't know what part you are referring to with "Rubber Cushion", but I assume it's one of the two rubber bumpers on the bolt. If so, no worries! Paintball-Gateway should have what you're looking for:
Shows it here. Odd name for it but you get the point.
Oh! Yeah, it's odd that Proto used the term phrase "soft rubber cushion", because that part is now known as the "bolt back bumper" as per their parts kit and key part name for replacement. That's probably why it wasn't ringing a bell in my head, hah. But anyway, PBG has what you're looking for and then some: