I just installed the OEM hitch that I bought at www.subarugenuineparts.com 
on my 2005 Forester XS.

Hoppy Lite-Mate appears to have made the OEM trailer harness as their name
is on the cover.

There is a picture here http://www.kwikhitch.com/wiring/subaru_wiring.htm

Chart says 63855, mine looks like the photo 63255 with special grommet to
pass through tire well.

Other charts give 33855, odd how the first two digits varies.
http://www.hopkinsmfg.com/twkits.html

Another photo http://hitches4less.stores.yahoo.net/suboutandfor.html

The connector only has a cross-like symbol that may be the Sumitomo
trademark on the back and "Y07" molded into it. I have not come across a
connecter like that before.

I did look around and found this much information on the Delphi automotive
connector site:

090 Series Terminals

Delphi Connection Systems .090 Product Line is a series of box-and -blade
electrical connection systems based on a standard male blade width of 0.09
inches.

These look like the pins,
http://www.delphisecure2.com/del/attachments/Image/090SeriesTerminals.gif

     Part Number:  13533981
       Description:  6 Way Natural 090 II Unsealed Male Connector Assembly,
Max Current 20 amps

They have a drawing but is tif file you have to download. The drawing does
give a Sumitomo part number of
6249-1225

I'm pretty confident it is a Sumitomo part being it is a Japanese car and
the symbol on the connector. Their site is here:

http://www.sewsus.com/welcome.html

This is as close as I could find. Wonder if you call Subaru and ask?

Take a look around www.delphi.com and maybe find a match.

With a price like that for the OEM harness, I guess what I paid was not too
bad. I looked at all the other options and I am glad I just went with the
OEM kit.

Good Luck,

Blair