https://www.fedcoseeds.com/trees/?cat=Scionwood has some; order early. At the moment they seem to have dropped plums and ALL of the pear scions (bottom of page as of 11/5/2017) they offer are perry varieties!? They are a solid company but in Maine, so if you live in a warm climate, theirs may not be the best adapted. You can usually order small numbers of sticks from the USDA germplasm repository in Corvallis, OR, which has some really obscure types, not only delicious heirlooms, but also crazy mutants with striped bark & fruit (Bon Louise
de Avranchees Panache or something like that; dessert fruit but fishy smelling blooms), red fleshed pears (mostly summer ripening & poor for storage) and one
apple pear (Pyrus pyrifolia) from the Russian Far East that is as acidic as a lemon (and called a "rootstock pear," but I would cook with it as I find most Asian pears too bland and in fact welcome acidity). They have reorganized their search page and I find it difficult to use now, but they do stock fireblight resistant and low chill varieties if those are relevant to you. I suspect Asians will be more compatible with Callery
roots than are Europeans. They have both. They even have sorbopears if you want to go really weird (but those have different looking foliage, so you lose stealth in your guerrilla campaign).
Unfortunately while I am better at budding than whip grafting, nearly everyone ships just dormant scions for the later (winter and earliest spring) because of
course dormancy helps things survive transit. Browse now & order early