eff it...I'll take a shot based on what stylish big friends of mine wear.
I'd look into a good quality tailored blazer. If you dropped, say, $600 including tailoring to shorten sleeves etc., you'd have something you'll have for a long time and can wear in any situation. Since you probably don't have easy access to lots of good stores, I'd go for Brooks Brothers' Web site.
This is available in up to a 48 (you may be bigger), but is an example of something that might work for you. :http://www.brooksbrothers.com/IWCatP...=§ionsize=
Pair that with a pair of medium-wash jeans (no gimmicks, please) and a nice white shirt and you're money. Interesting eyewear and a vintage military watch would add interest. I think the goal is to not draw attention to your middle. Alternatively you could wear a khaki cotton sports coat. at 40/32, you should pay attention to the pant/shoe interface. You don't want your pants to swallow your shoes...you might have to have a tailor taper your jeans an inch or so.
If you're bigger than any decent OTR sports coats, I'd seriously think in the future about going MTM or custom made.