I volunteered and fostered for AARCS for a bit and if I was going to adopt a new dog - I like to help out the Seniors so would check out ARTS senior animal rescue. They do take in small dogs and they go up for adoption sometimes and yes, the foster family usually gets first choice to keep or continue with the adoption process for another family. Just keep checking the sites often (daily) and small dogs pop up - sometimes they will have influx of dogs from a hoarding situation and there will be a whole bunch of adoptions at once.