I think you will need a 5-4 wire converter Don. They are easy to find in motor factors/auto parts shops.
EMC and California trailer wiring colours are (as far as I remember):
Red - brake light power
Black - accessory power
Brown - running light power
Green - right turn signal power
Yellow - left turn signal power
White - ground
I know this has been discussed here in the past Don, you should be able to search for the threads. Some of the other members may pop in later with more information.
I highly recommend using the easy button on this...
I too have an Aspen camper trailer, and got my harness from Cycle Max. They (and other M/cycle stores) carry in stock the harness you need for your model m/cycle, and it's a simple plug-n-play install... Could NOT be any easier than that.
I researched going the autoparts store route, but discovered that in the long-run the purpose built one for you model bike, will be less expensive than chasing around your local autoparts store for a "universal" type adapter, that you have to modify (cut to length, add terminals, etc.).
Use a trailer isolation harness that uses relays and power off the battery to save over taxing and possible lights blowing bike lighting circuit on the road. It's plug and play off the bike and just have to remove left saddle bag and trunk bottom then wire your 6 pin outlet. My outlet is mounted down on the hitch with the metal bracket. I have seen them mounted in the rear fender but I'm not a fan of that.