Auto paint shop should be able to tape and paint the hubs but the cost might be a bit much since they have to apply the tape which takes time if done correctly...and there is also the possibility that they might not be too careful and you'll be disappointed.
A number of us have painted our own hubs. I did mine last Winter.
There are messages here with detailed step by step photos for Do-It-Yourself hub painters. Takes some flexible masking tape, a rattle can of paint, and a bit of time. (The hub color should match the hard top color.)
There is a Stencil for the older 230SL two part hubs...not sure if the quality is as good as using tape.
Richard M, NYC