Excellent advise from Summerrain and Odile!
Whether from a reputable breeder or from a rescue, adding a dog to the family is not something to be done on the spur of the moment - both options involve advance planning on your part, and scrutiny of your suitablility as an owner on the part of the breeder/rescue - this takes time. From top breeders multi-year waiting lists are not uncommon. And as per Odile's post, many rescues are very wary about holiday time adoptions - as the old adage goes, 'A dog is for life, not just for Christmas'.
Any breeder willing to hand over a puppy right away is not a good breeder - most likely a battery farmer. Do not support this vile industry.
Another option is to look for a breeder or breed rescue in Germany; the same planning and scrutiny will be required, you will find the same wariness of holiday time adoptions. The German version of the SKG is the VDH ( http://www.vdh.de ); to find a breed rescue google something like 'chihuahua in not'.
Be aware that you would need to comply with import conditions if you buy or adopt abroad; see the BVet ( http://www.bvet.admin.ch/themen/0161...x.html?lang=en ) for those requirements.
Also, get in touch with rescues to let them know that you are looking for a chi should one come into rescue in the future. Get to know the staff, give them a chance to know you. This is what I have done - my favorite breed doesn't come into rescue too often, but all the breed rescues in Germany and Swiss general rescues local-ish to me know that I'm a sucker for ancient, broken, or psychotic shelties and collies.
In addition, are you a first time dog owner? If so, you will need to do the theory portion of the SKN before you acquire your dog. The theory course is 4-5 lessions, usually done at the pace of once a week, although there are trainers who provide different schedules. A good breeder or rescue will expect you to show proof that you have done this before you can take your dog home. If you fall into this category and have not yet taken the course, get that done before you even start looking for the dog, especially at this time of year when many training schools close for the holidays/winter.
All owners, first time or experienced, are required to take the SKN practical course within the first year of ownership with each and every dog you add to your family.
Wishing you and your future four-footed friend all the best - and a good start to a lifelong commitment.