10-18 months old AND KC registered? Hmmm. That's hard to fill from people who raise puppies. Usually they're long in their homes by then.
Are you looking for Drug or Bomb detector training? Just curious, since neither really requires size or specific pedigree to do the job. Beagles are being used in many airports to detect "contraband" for customs. :)
I know in the US, police get their dogs from several sources: Shelters are usually the best place to locate dogs, since many people give up their dogs around a year old due to behavioral problems. 1 out of 4 dogs in the shelters are large breed purebreds with AKC papers. Ex guide school dogs are another source.
good luck (I think)
toodles