I have a similar problem but get the suit adjusted after purchase and it works out well.
I’ve been very impressed with Charles Tyrwhitt suits. Good materials, working cuff buttons, non fused construction. You can also buy seperates and lots of sizes, so get trousers that fit your thighs and then have them adjusted at the waist. Anything under a 4 inch reduction at the waist should look fine – I’ve gone from 36 – 32.5″ with no problem.
Don’t get the slim or tailored fit imo. They just look at bit amateur hour.
TM Lewin also a good shout.
Use quidco for an additional discount.