I haven't heard about semi-focused plasma cleaning being commercially available for SEM or Microprobe, but this is really a straight-forward engineering project. I agree with previously posted discussion in that the most logical place to locate such cleaning is in LLK, while cleaning sample immediately after pump-down and prior to transfer to the main chamber. Market is probably too small for making blank-page design, but adapting ion gun from existing ion mill (Fischione, for example) would be straight-forward. For "proof of concept" just place ion gun above sample location in LLK, for more sophisticated approach make some crude X/Y in-LLK positioning. As cleaning is done in LLK Ar poisoning of ion pumps is, probably, of not so big concern. Also, there is no any reason why ion mill gun wouldn't fire with H2, providing that backpressure/gas flow/power parameters could be varied. I'd happy make such retrofit, providing there are adequate money behind the interest. Or try talking to Noel Smith of Oregon Scientific - I bet his team would be more then happy to custom-make H2 plasma column for your load lock....