As Kreuzfidel mentioned, tailoring is always an option (and probably the best option with a persistent problem such as this).
Try and see if anyplace around you that sells clothes offers tailoring -- or, if you can afford it, you can find a tailor specifically -- some places even offer free tailoring. A lot of articles I've read about clothes/men's fashion/whathaveyou actually recommend tailoring. It tends to be an exception to the norm for something to fit properly right off the rack whether one's cis or trans.
Not sure your exact situation or body type or anything, so I don't know whether this is a viable option for you as relates to your dysphoria or anything, but it's probably the option with the least headache and the least time-consuming if it's a possibility for you. It can also be used regardless of what item of clothing you're purchasing or struggling with.