Have you tried blog comments? If you have something on your site that can give value to a blog post, you can share your link there. You can use Google to look for those blogs. Just a peek at the different search operators would be helpful.
yes I have looked on google but unfortunately when it comes down to the industry while there are blogs they don't allow comments or guest blogging at all.
the only thing i can come up with that would make sense for this site would be that the point of sale software uses a lot of open source software such as apache webserver and hadoop.
I have always had the same problem, most of the sites that are truly relevant to mine are competitors. The problem is that if I broaden it, even if I think a site is still relevant Google may not.
yeah that's a challenge. i got the problem with that as well, really frustrating especially when they got higher ranking by getting links from car insurance websites.