Seek out your local carpet cleaning distributor. They are going to have a lot more options for general cleaning as well as specific stain removers.
But as Mark said, not everything can be removed and you need to set realistic expectation upfront. If you've been doing this for 2 years, I'm sure you already have a good feel when you look at the carpets that something isn't coming out.
I used to think that if I told a client that something couldn't be done or would not be perfect that I'd look the fool. In reality, it's far worse when you don't deliver on the expectation. You look more professional when you mention that something likely cannot be removed safely and explain why.
way off topic example: I started a car last night; when talking through the issues with the owner we noted a bunch of dried wax at all the clearbra seams. I said I would work on it while the touch-up paint dried, but that care needs to be taken not to lift the CB or dissolve the adhesive. As such I may not be able to remove it all. There were a couple spots that I couldn't remove because the CB was already peeling back a little. Owner was very pleased with the results.
specific reasons it may be unsafe to get a stain out: over wetting carpets or upholstery (mold/mildew), damaging fibers/nap, dye transfer from carpet or upholstery.
