Before anyone comments on this machine, it is not mine, I am trying to fix it for my mother.

I need to replace the steam valve, it is now so bad, nearly half a cup of water is lost out the steam wand before a single shot of espresso can be pulled. When I opened the machine up, it looks bad. The steam valve appears to be pressed into the boiler (nothing appears replaceable, thermostats, elements etc), it is all a single unit. Does anyone know if the valve can be removed and/or replaced independently of the main boiler assembly? If not, any ideas where I can buy a new assembly or is this just being silly and we need to write the machine off?

Regards
Ben