
LOL 100's of places ;)
Depends on what make & type of car, whether you want it to be a permanent fixture in the car or for use out of the caras well
I've got 8 crates
One is a lintran transit box that is in the car permanently(it can be taken out of the car of course), one small crate in the lounge for the cavaliers to use if they want, one huge one in by bedroom that my BC sleeps in(big enough for a GSD plus a couple or three BC's, One large show crate, two smaller ones that I use for the cavaliers after bathing before shows & two old car crates that have been stored "just in case";)
They cost from £500+ for the lintran box to under £20 for the single cavalier sized one. They have been bought at shows, over the net & from the manufacturer(Lintran)who fitted it in my car
If you are going to any Championship dog shows like Crufts, Leeds etc, even some open shows you can "try before you buy" well at least see them, Pet warehouse stores etc
I would advise to have a good at any crate you fancy & check them for rough edges etc
They come in all sorts of designs one & two doors, my transit box has an escape hatch at the back, another has a top & a side door