Just in case anyone else is interested, according to Vango, the side canopy from the Tigris 800 is not a bad fit for the Oregon 800. Apparently it's not perfect, but should be ok.
My tent, an Outwell Oregon, does not have a canopy/ porch made for it. So we have a Coleman canopy which is an OK fit with a bit of tweaking. What I am trying to say is, if you can get a porch that will fit your tent,i.e it's wide enough and high enough to cover the door opening, it will be fine. It does not need to be made to measure to work.