That GT-40 window is a toughie. I once had a similar scenario, and I mixed up a 50/50 mix of Elmers glue and Tamiya black acrylic paint to make a black windscreen sealant. I applied it sparingly all around, set the glass in place firmly, and carefully wiped away the displaced 'sealant' with a damp cloth or tissue. It worked well.
However, as seen in your reference photo, the GT-40 has no sealant or gasket at all. My first thought was as Peteski suggested. Carefully drill holes through the glass and frame and use a fine wire (I like guitar string) to hold the glass in place while representing the screws of the 1:1. This will require a small bit, maybe 1/64 or #78 or so. As mentioned above, small drill bits is no place to scrimp on money, and good ones are expensive. I buy them in packs of ten from industrial suppliers. Cheap ones are not worth having, and that's not just being pedantic. They will ruin a delicate drilling job, and this one would be a delicate drilling job. Get a good comfortable pin vise, too.
Don't try melting holes through with a hot wire, etc. The hole size will be difficult to control, as will it's exact location. It will also create a bead of displaced material around the hole that will need to be removed. It would be very difficult, if not impossible, to do it neatly this way.