Unfortunately most of the sites I use are being blocked to the US by litigation on the UK suppliers by American publishers.
Here are a couple others
www.karaoke-version.com - best bet right now and incorporated in Hoster with link
www.karaoke.net - fairly new source but steadily growing
www.allstarcustom.com - hit or miss quality but sometimes have something no one else has.
https://www.karaokeclouddownloads.com/ - a lot of old Chartbuster library rebranded Karaoke Cloud. New stuff leaves something left to be desired.
limited access to music
www.sbikaraoke.com (not all songs are available as download and they no longer ship custom discs to US)
www.selectkaraoke.com - this is actually the company being sued by Sony/EMI directly - all the other UK manus have also been added to this lawsuit. Credit only system, pre-purchase and use credit per song.
I buy on an as needed basis (provided it's available). Cost depending on where you buy from are usually $1.99-2.99 per track.
There are no 'legal' sites to subscribe to monthly for downloads. And the streaming sites are only locked into the suppliers own content and requires their own player only.
Most are mp3g, zip or video files that will play in Hoster. If you download on the fly - download to a separate folder, you can play them directly using the k-oke, or video (depending on which format the download is in) - select the download folder & pick your song. It will load up to the playlist & you can add singer name then!