Get a VPS, scrapebox or gscraper, you can scrape yourself with many footprints shared here on BHW. You won't meet much duplicate sites if you have your own keywords mixed with footprints.
I've tried buying various blog comments gigs on fiverr, for as many sites lists as possible. But guess what? ALL of the gigs have duplicate comments. Which means for 100k blog comment backlinks, you could get backlink from like 5-10k (10k is generous!!!) domains.
So it's at best if you could spend some time viewing some scraping tutorials, get your footprints, learning about scraping, or you could spend (a lot of) money to hire a guy to do scraping just for you (while with a VPS and proxies, you could run a lot more stuffs on it).