if you go on Hobby horse's website (can't remember it right now) they will have an area where you can find international sellers. I really like Hobby horse clothing and they come in plus sizes(which is what I need) they just usually need to be ordered in from the closest dealer or right on their website. I mean if you read instructions and be honest with yourself when measuring, internet shopping from them is pretty easy, and lots of there stuff is on sale right now so its a good time to buy.
I believe they come in a variety of sizes. I haven't boughten from them yet but my riding instructor does and she has no problems and she was around the same size as me. I believe the sleeve sizes depend on the style, they have several styles and the clothes I have worn (although they weren't mine) fitted me fine and I have long arms and legs. I would check there website and see how close you can get to you sizing.
I bought all my show stuff there. I have 3 candy apple red rail shirts, candy apple chaps, black chaps, saddle and bridle with bit ($120), and show pants. I spent only $200 for all that.
I ordered sewing patterns from www.suitability.com they have western show patterns for everything from shirts, vests, jackets and even for fancy cutouts to adorn your shirts...and they also have english sewing patterns. I'm not a great seamstress so I'll have them made and then embellish them myself with adhesive crystals. Lot's of ideas on their gallery pages to provide inspiration.