Radiohead,
The once plentiful mid-1970's DPM Combat Uniforms have become increasingly difficult to locate. And when you do run across them, they tend to be in "Size 4" (medium regular) and faded/frayed condition. Your best bet is to search eBay "Collectibles, Militaria" on a weekly basis using the search words "Camouflage", "Camoflage", "Camo", "DPM", etc. They occasional set turns up for sale there.
There was a mint condition shirt for sale at "Westley Surplus" in New Westminster BC for $50 when I visited this July. They may still have it on the rack. I was tempted to pick it up as a spare trade item, but had higher priority purchases at the time. Try Canada 411 for their number, as they don't have a web-site. You may have to give the owner a link to the "North America" page of web-site so that he sends you the correct item rather than some generic Brit DPM.
Do a search on this site under "Para Smock", and you should find a lengthy past discussion regarding the development and use of the Canadian DPM Combat Uniform. I covered its history in relation to the Canadian DPM Para Smock. The uniform was produced by Peerless Garments for the Tanzanian Army circa 1975. It underwent wide-spread trials in the Canadian Army during the mid 1970's, but was rejected as a result of inadequate performance in comparison to the existing OG combats. Canadian surplus stores were full of mint condition contract over-run uniforms in the late 1970s/early 1980s, but unfortunately those supplies have long since dried up.
Good luck in your quest.
Cheers,