I agree with Ray, lowering the bike even further from the already lowered stock configuration is a bad idea. Not only will it negatively affect comfort, it will further reduce ground clearance and cornering clearance, which translates to a possible safety concern. If it were mine I'd forget the ego thing and just get a good pair of riding boots with a thick sole and heel, and if that wasn't enough I'd look for a better seat with a lower and narrower front section.
Harley does not offer a lower shock option than what comes stock on your SERK, which is already the Low Profile shock from the catalog. I'm sure you could find aftermarket shocks to do what you want to do, but I expect you would find what many others who went down this road found. It's a waste of money that results in a lousy ride and other problems. If you are determined to lower the bike anyway, check out one of the air suspension kits on the market with an onboard air compressor. Those will allow you to drop the rear of the bike for parking lot maneuvering and then pump it back up for proper handling and clearance while riding.
Jerry