The ECM Jazz label is one of my favorite labels so I am always on the lookout for music in a similar vein.
My current favorite download service is Bandcamp.com. It has always supported FLAC lossless downloads and even High Resolution Audio in the form of 96k/24b FLAC. Sometimes these are available for free or at a low price.
I devised a google search that will find artists who have a "Name your price" and ecm and jazz on their Bandcamp page.
Just use: "site:bandcamp.com "name your price" ecm jazz"
There are some nice things out there to find!