I have bought 25mm wheel spacers from kseriesparts before by H&R? They should have a set for 15mm. Also I am selling my four spacers in case anyone here wants some spacers!
They do have 15mm spacers for the RSX on kseriesparts, but not the bolt-on type. They only have the type where you have to do extended wheel studs. I prefer not to have to swap out the wheel studs if possible because it's a bitch to do. It looks like they do have 15mm bolt-on Eibach spacers for sale on kseriesparts but the center bore is not the correct size for the RSX.
I have found "Stance Magic" brand spacers on Amazon that are the correct specs (15mm bolt-on, 64.1 bore), but they are very cheap and that scares me. But then again, those could very well be the same ones that DC5Rparts guy is selling for a huge markup. I don't think his were branded, so who know what they are.
Oh well...maybe someday I'll feel like tackling the wheel studs...but not today, lol.