I really don't consider myself "plus-sized" as I'm a UK size 12, which is fairly average over here, but in Japanese clothing (especially lolita) this is what I'm termed as. Personally, I'm really happy with my body the way it is. I don't want to lose weight just so that I can fit into some tiny (but beautiful) clothes because it's not worth the upset, frustration and disappointment that it causes... I've been there before. Honestly. So, I've decided that as my sizes fluctuates between 10-14 - and even when I'm a size 10 those dresses were far too tight, especially around the bust area - I'll have to choose lolita clothes carefully. Browsing through the internet, I've found some useful advice:
Find JSKs with either full or half shirring around the bodice. Believe me, it will give you room to breathe! Being comfortable is one of the most important aspects of fashion, so forget that "beauty is pain"! The shirring is especially vital if you're large around the chest area...
Some people say that quarter/partial shirring is friendly for plus-size girls, but I have to disagree in my own experiences. The corset lacing on the shirring makes it harder to breathe in, and may cause tearing in the fabric and lace if you're even just a little bit over the measurements.
So, in a nutshell, full or half shirring is your best friend! Get blouses and JSKs with as much shirring is needed. For example:
Cutsews may be a good alternative to blouses as they're stretchy and may provide more room. They can be as dressed-up or as dressed-down as you want, so will suit many different styles. Also, they're much cooler in summer months.
If you're not certain that cutsews will fit you, why not just wear a cute T-shirt instead! It would look great for casual lolita, and you could always make it more loli-able by using tutorials on the internet to pimp up a T-shirt by adding lace, ribbons, capped sleeves, a peter pan collar or a yoke, for example. Just be creative!
3) Boleros and Cardigans
As boleros and cardigans don't exactly have to meet in the middle, and can be made of stretchy material, maybe they could be worn by plus-size girls? If it's comfortable around the arms and shoulders, and isn't too tight in the chest area, I think it would be okay.
This may only apply to some girls, so don't worry if this isn't for you! You could always buy cardigans and boleros from high street stores in cute colours. They are fairly common, and again, can be customized to your own tastes.
If the problem is in the bust area, you could always wear lolita skirts. Some skirts may also have an elasticated waist band. Just look out for skirts with a corset-like waist, as they will be tighter than the usual, standard skirt cuts.
5) Brand accessories
If all else fails and you're completely intent on having some brand items, you could always buy accessories such as bags, head bows, bonnets, socks, gloves, etc. These items are still unmistakably lolita style, and you don't have to worry about them fitting you. Plus, they're not as (*cough* ridiculously expensive *cough cough*).
6) Tailor-made items
I always think it would be nice to design your own dress and have it made by a professional tailor. They would make it to your exact measurements and it would be unique and special to you. Also, you can decide all your own fabrics and components, which is always exciting. Besides, wealthy Victorian ladies always had their clothes specially made by a tailor (and so do royalty!).
7) Altering existing items
Apparently even Japanese lolitas have this done to their brand items to give them more room. There's nothing wrong with altering clothes if it will make you comfy and happy. If there's a dress or blouse that you can't live without, you could always alter it and still wear brand. However, don't do this if you're not a confident seamstress! Hand it over to a tailor or seamstress so they can see what they can do to make it fit better.
I've heard that TaoBao shops can make dresses to your measurements. Just be wary of certain shops on there and know that you're going to have to use both a shopping service and a Chinese translator. You can look at how to use taobao on hellolace.
9) Choose clothes carefully
Know your measurements and dress to suit your shape if possible. Of course, this isn't too important, just make sure that you're happy and feel right in your clothes.
10) Final advice
Don't care about what other people say about you. I know that some people (especially in the lolita community) can be nasty about plus-sized people, but just remember that you are beautiful anyway! Beauty is inside, not outside.