there is a guy or two in tampa that does them.
i use extremeturboshop.com they are out here in lakeland, 863-647-3700
they did a good job rebuilding a turbo of mine about 2 yrs ago.
just FYI, you cannot rebuild a ball-bearing CHRA (center housing rotating assembly). so don't expect it to be cheap because you will basically be buying a whole new turbo, just without the compressor and turbine housings. it may be in your best interests to find another used turbo or buy new.