I can't find any legit ways to purchase it yet, other than Apple Music and their shit compression. I normally get my digital music from 7digital because they offer FLAC files and it's not up there yet.
On your Iphone… go to Settings - > Music - > Audio Quality
From there you will be able to adjust to Loss Less Hi Q. Also when you download tracks, you can download them in lossless as well - streaming is not set to lossless due to big data usage.
ALAC up to 24 bit/48 khz and higher.