It is very late in the season to buy geese. They usually lay only in the late winter and spring. You may have the best luck checking craigslist in your area to see if anyone might be selling older goslings.
I raise white Chinese geese and I would offer you some if I had babies but unfortunately my geese aren't laying right now and probably won't again til next year. Goose season usually runs from April to June. Geese lay 50 eggs or less per year so their breeding seasons are a lot shorter than other fowl.
you can check here on BYC there is a buy sell area. In that area there is a section for other poultry and at times geese listed there for sale. This time of the year would be adults or juveniles listed there for sale.