Howdy and welcome :) I used to own one of these and it made a fairly good coffee.
Diamond C are no longer unfortunately and I am not aware of anyone else having picked them up as an agency.
I would suspect you need to lubricate an oring or two on the steam wand or even replace them, a good industrial supplier for some viton orings and a tube of food grade grease and do it yourself I reckon. If you want genuine parts then get onto espressoparts in the USA and get a non pressurised basket and a spare group gasket while you are at it. Getting the machine apart was a little awkward but easy to do with simple hand tools.
Due to the lack of spares locally and the relatively low cost of the machine there will be some reluctance for a commercial person to look at it too.