Princess JessieKate
Depending on how plus-sized you are, you could fit into fully-shirred pieces from anywhere that stocks them including brand name stores. Bodyline carries some pieces in sizes up to 2XL. I think they also carry sizes up to 4XL but only on their wa Lolita pieces and I really would advise you to stay away from those. Some Taobao stores will make custom-sized pieces, as will Anna House at annahousefashion.com. You could also try buying used from the Plus Sized Lolita Sales community on Facebook, but a lot of people there sell ita stuff and the mods don't do anything about it, so make sure you know what you're looking for.
There are some dresses that are 4L. Some of their 2L's actually have more like 4L sizing. It's all over the place. You just have to look at the measurements.
Usually about a US size 20-22 seems to be the point where finding things that fit from most Japanese brands. Some full shirring things go higher. I have a few friends at that size who wear a lot of AP/Baby/Meta. You'll have to do custom-sizing after that point.
smile