I would second the idea of getting a local welder or engineering shop to make up something suitable. If possible send it off for galvanising which they can do too.
Note many of these larger dishes are not designed to use normal TV LNBs but are instead intended to use special manufacturer feeds, and they use unusual designs. Using the wrong feed will reduce the results.
Here is information on the recommended installation in a fixed mount including concrete base.
http://viasatelital.com/manuales/channel_master/channel-master-type-120.pdf
If you are not using it in a fixed position, but for low earth orbit tracking on s-band, like I am, I can give more advice. I am using a 1.2 metre dish. In particular the modification for larger feeds, calibration due to offset feed and real world low earth orbit tracking problems.
If you can supply photos of links of the actual dish we may be able to help further.