even if you could buy a bolt on air con kit it wouldnt be worth the cost. It would be a lot cheaper to sell your motor and upgrade to a HLX, then you get heated seats, front fogs, a rear spoiler, and many other nice features too!
Or even better, get a HGT with Air con, heated seats, a gorgous sound when you go along, loads of power and a beautiful looking car. (Sorry but im still in love with mine, ive only had it two weeks!)