Getting air conditioning installed in an old car

We bought a car in the fall rather urgently and were told we could get A/C added in. Now the dealer is telling us they can't do it. It's a 2005 Citroen Xsara Picasso. I'd like to keep it another year but really need A/C to get through the summer. Anyone know a place that may be more creative in helping us than the dealer? Also fine with it being in NL, France or even London as we'll be driving there soon.
Cheers