Check out clickmix.com – they carry a lot of the tracks from dynamix and powermusic, as well as their own. You can buy individual tracks and they will mix them into a custom, seamless mix for you. Get exactly what you want instead of settling. I am a 100% satisfied customer for them. I’ve used them for probably 80% of my class music. They charge $1.99 a track and have controls for tempo and mixing so you can flow between tracks. It’s really a great service.
Also, check out DJ KJ’s free podcast on iTunes. He also sells fitness mixes on his website, but he gives away a lot of his mixes free in his 60 minute uninterrupted mixes through his podcasts. https://itunes.apple.com/us/podcast/dj-kj-podcast/id548458764
Also Studio rat music (www.studioratmusic.com) will make one off custom mixes for you. It’s not cheap, but if you want something custom (a mash-up maybe) this is the place to go. This is where all the competitive dance recital teams and cheerleader squads go to get their custom competition tracks.