I have a BrewersHardware sight glass and ordered the 1.5 from them and gaskets from Glacier, but the boro glass part's O.D. is larger than the tri-clamp flange. Put the 1.5 gaskets that look like they were cut with a pair of kids safety scissors in and the fit was not perfect but i pressure tested my MKIII to 105psi and put in a horse trough and saw nothing. Then pulled a vac under water and it sat for several hours. Not ideal but have done ten runs and will be putting the 2" gaskets in today or tomorrow because it is the right thing to do. Paramount may still have GW's blank but sounds like they could solve our problem for a nominal fee.
I believe that they used a standard die, because it only took them about 15 minutes to make them and it was under $20.
I handed them the silcone rubber gasket out of the sight glass and told them to cut me a dozen out of Viton, in a similar thickness, without the raised ring around the outside.
There is their link: http://www.paramountsupply.com/