Try this for Stems if you have Ableton!

If you have Ableton I found a cool method of exporting stems and creating my own.
Just download (well buy) templates for Ableton and then you can switch up the sounds and parts to your liking, even change bpms.

The best site I found was Abletunes, it has a decent selection and doesn't use too many extra plugins, mostly Massive and Sylenth. Other sites are out there but use all kinds of extra plugins that can cost a huge amount of money. Loopmasters also has some.

Combine this with a sharing site as mentioned elsewhere "Dubseed". More selection could become a reality.
The key of course is knowing Ableton workflow a bit.

The nice thing about a template is the structure is already there and you can remove or add and not need to go through a ton of tries for just one sound. I have yet to make all I want due to time but this will be much faster than taking weeks or months on a track and not getting the style correct, but still give a unique sound, plus the grids are perfect also so no problem with sync.
Yes the templates are a bit pricey, but hey someone else has done the hard stuff, plus you can make many tracks from just one.