I'm not sure where to find a cheaper motor, but if possible, you'd be better off switching to the Canadian LX style manual seatbelts. You'd need the seatbelts themselves, new B-pillar trim (with holes for seatbelt mounts), and the lower seatbelt mount. You'll be much happier without the motor belts, believe me
If you want to see pictures of the seatbelts, check out my car gallery here:
http://community.webshots.com/album/34068726JPuQCL