There are numerous companies offering different levels of commercial support ranging from a full WBEM server implementation to limited consultancy. I have just used Google to search for the keywords "wbem consultancy" and had 280 hits, most of which, according to my unscientific sampling, appear to be consultancy companies offering support for WBEM.
Whether or not commercial support is required for your project is, of course, a decision that only you can make but here are a few points which you may wish to consider:
As you can see from Chapter 9, creating your first CIM model is not trivial. Determining precisely what your classes are and where they fit in the DMTF's hierarchy is not trivial. Consultants, familiar not only with the results of the standardisation process (the standards) but also with the discussion which went on to reach those results, can be invaluable.
Many commercial companies offer the service of taking the open source software products and charging for a more controlled release cycle, thorough regression testing, emergency bug fixing and better documentation. This may be a suitable half-way house between true open source and commercial products.
Some of the commercial WBEM servers have been developed for a specific market which might match your requirements better than a general-purpose WBEM server. There is, for example, at least one C-based WBEM server on the market which has a much smaller memory footprint than any C++ or Java implementation.