Some products will work, but literally require re applying nearly weekly. Autoglym Bumper Care is the only one Ive used in the past(on a Punto bumper) and it really just turns it from light grey to a darker light grey. Youtube using a heat gun on faded plastic, but even that is only a short term solution. Best bet is to look for a set of trim from a face lift civic as they were all painted Galaxy Grey. Or if you can find an Si model painted the same colour as yours, as they were colour coded.
I have recently been trawling through old threads looking for something to restore the colour of the faded grey trim on my '07 Type S. I came across a product called Plasticare trim dye which some members had used quite successfully. Unfortunately it doesn't seem to be available any more. It seems the next best option might be Wurth's plastic dye. I'm going to order some soon, for when the weather improves a bit, I think it's available in grey but I'll be trying the black.
I've tried various products supposedly made specifically for this job, but to be completely honest the latest one I came across has been the best so far by a mile and its not even a car specific product.
Ronseal Teak Oil, yes you read that right, Teak Oil. £10 buys you a big tin of the stuff which will last for ages. I applied some to my exterior plastic trims way back sometime around October/November and after all the crap from winter driving and several washes the trim still looks clean and tidy.
Laugh if you want but this stuff works a charm and is comparatively cheap next to car specific products which may not even work as well.
I highly recommend Solution Finish for turning trim back to a dark black. I've used it myself and it's great and lasts a long time if you keep the trim coated in a good anti-uv coating like 303 Aerospace protectant after application of SF.
£15.99 gets you a laughably tiny bottle but honestly this stuff lasts FOREVER as you'll only use drops per application and it's spreads a huge distance. My advice is also to apply using a a tiny piece of cut foam which won't trap excess product like microfibre or cotton pads can.