I am a 54inch chest (just big and fat) American stuff tends to be made in bigger sizes. I personally wear tiger Stripe most of the time.https://www.military1st.co.uk/ is good for sizes and range. Helikon stuff is pretty good quality for the price and flektarn is good camo for British woods.
Your best bet if you want desert DPM is look for a smock as apposed to shirts or UBACS as there ment to be worn really baggy so you get them in that sort of size ranges .