I looked around for trailer hitches.... both the Subaru and others. My dealer quoted me $225 for the hitch, subaruwrxparts.com had it for $175 (without shipping). I checked at trailer-hitch.com and they had a Draw-tite hitch for $89. For $125, I got the ball, the draw bar, and the hitch including shipping to my door. I used a 4.99 wiring harness from the auto parts store.
The hitch fits perfectly, NO plastic cutting required. Took about 45 minutes to install.

Oh, and for a trailer, try a utility trailer from Harborfreight.com.... I got one for $239 (free shipping). I had to assemble, but it took about 3 hours. Folds up, you can stand it vertically and roll it around, almost takes up no space (4'X8' trailer). Comes with lights, trailer harness, and car harness. $30 for the California PTI and I'm on the road. Tows well, 1000lb capacity. Even has the brackets for you to make a stake bed out of 2"X4"s.

Good luck

Brust Roethler