Yes: Check out ebay seller 73mustangconv
https://www.ebay.com/itm/BMW-E90-F10...V4UKR&LH_All=1
His harness has higher quality RCA connectors compared to the Technic harness. The harness doesn't come standard with a relay, that is $10 extra per the description in the ad but there is no need for a relay even if your connecting 2 or 3 external amps. The coil on some relays will pull upwards of 200ma from the remote out which may be more than the total remote amperage draw from several amps combined. Just pigtail off the remote wire as needed for amps, DSP, Etc. For those insisting on using a relay make sure you have a flyback suppression diode wired for your relay.
He sells a basic version for people who want to run their own speakers wires from their own amps.:
https://www.ebay.com/itm/BMW-E90-F10...V4UML&LH_All=1