First is where one obtains castor sugar. A lot of the sponge recipes I come across calls for castor sugar (aka baker's sugar), and it's an item that's difficult to track down. I think I can get it from Amazon (in a 4-lb package), but was wondering if there may be alternatives.

The next is a recommendation of a baking pan (relatively large-sized) for baking said sponge (goal here is so that I can cut the thing in half and stack the layers). Something that will stand up to the baking temperature without deforming. Also looking for something without any fluorinated polymer coatings.

Would appreciate suggestions on either of these.