I think I'd buy a 2nd hand factory light before I'd put a Chinese job on there. The Chinese like to use ABS in everything; it's cheaper then Polypropylene and about half the strength.
If all that's wrong with your light is a scratched up lens, you can buff it out with plastic buffing compound with not much difficulty. If you've got cracks on the Polypropylene housing, you can glue it with Loctite 3035. It's designed just for Thermoplastics. Its not cheap but is about the only thing that works for that application. You can find it online or at Grainger's but you won't see it in standard hardware stores.