mig - there are places in the city that can fab one up, but will cost you $$$.
any reason for the cage? rally? drag? cosmetic?
any hardcore cage will result in you losing the back seat.
I would recommend the STI cage, but it will be pink =D There are a few places that offer a bolt in cage, but the legalities of some places (gimli dragstrip, wscc) might limit your options.
The car looked good at the WOW, i didn't have a chance to say hello as you were talking to a few people. I had the big blue subaru jacket on =D
first autocross is on sunday if you are interested. i hope to attend as well.