There are planty of comapnies in the UK who would do this, but basically they sell turbos off the shelf with this already done, so most likely they will just sell you a complete exchange turbo rather than convert yours.
You might be able to persuade one of them to do what you want, but I doubt they would offer any warranty on an unknown turbo. Then again, they would need the complete turbo, as the centre shaft would need to be rebalance with the new compressor wheel. This also means they have to strip and rebuild the turbo, so most likely new bearings etc, so the costs soon add up... You could save money by stripping the turbo yourself, and just sending the shaft, but what if it's warn or bent? You would still also need to replace bearings, so I just dont' see it as a sensible option. My advice is to just buy a hybrid turbo on an exchane basis, in the long term it will be worth it.