Geoff,
Sorry I cant remember who does the bellows now. We had bought some stuff a while ago but I cant remember who we got it from.
As for the extraction system a hose connected to the cutting head will not provide adequate extraction of the dust and fumes created by plasma cutting. The majority of the dust and fumes will be under the plate. The gas pressure from the cutting torch will push most of the fumes down through the kerf cut in the plate. I think your best idea would be to box the machine up and extract from the box area under the cutting table. Remember your filter as well. I think plasma cutters have a legal obligation to have filters fitted to them, particularly dry cutting plasma systems but i'm not sure about this. If you are extracting large amounts of dust into the atmosphere I dont think your neighbours would be too impressed with this. Water under the cutting table does reduce the amount of dust made by a large factor so this would help. Remember you can also plasma cut under wate as well with the correct torch and consumables.

Ian