This really is not a place that deals with Lepidoptera sales.

Cabbage whites always have some black markings. You could possibly have the native Margined White, closely related. The summer forms are all white with no black markings. The caterpillars of the margined white eat crucifers. You would have to be near an undeveloped area to have these in the city. Otherwise, look more closely for black markings. The cabbage white caterpillar also feeds on nasturtium.

I visited your fine website. Using the term caterpillar for the sawfly larva can lead to confusion for the average person who associates caterpillars with butterflies and moths, as indeed your website identifies its purpose. Although the term sawfly caterpillar is in common use, the term sawfly larva is used much more often. It is perhaps a minor point, but I am seeing a lot of unknown fly larva posted on various forums as caterpillars; there is a need for education here so that people can be searching for the proper adult forms rather than looking in the wrong areas of the Internet.

I just hatched out 9 Luna moth caterpillars in a tupperware tub a few days ago. I did have 23 eggs but only 9 hatched so far lol. I happy I got some though. Hopefully some of them will make it to adult size. I can't wait to see them come out of their cocoons! They are eating Sweet Gum leaves and growing quickly.