The following is essentially the same as shown in Post #3 above. It looks like IC made a tape hinge along the top edge—great idea.
Temporary Glass Carrier
You can make do with your film sandwiched between two sheets of window glass. I’ve done so with enlargers for which no glass carrier could be found. Determine the size you need and have two identical sheets of window glass cut. Deburr all edges and corners with a fine grit sharpening stone so that you can handle the sheets without cutting your fingers or damaging the negatives. You should also make a top mask that looks like a print mat. Make it of a thin black materiel. You can use a sheet of black construction paper such as is used for school children’s art projects, or you can use a totally exposed, developed, fixed, and washed sheet of enlarging paper. Thin resin coated paper works best.
Layout the opening you require with a pencil. I use a silver-lead pencil from an art supply store on black paper. If you make the mask from photo paper, you can do the layout on the white side. Use a ruler to guide the pencil. Then cutout the opening with a single-edge razor blade guided with a steel rule.
The mask serves two purposes:
1. Placed atop the negative before laying down the top glass, it prevents the formation of Newton rings.
2. It also holds back excess spill light. You might need different masks depending on the size of the negative. You might want to apply black paint or enamel to the edges of the glass to prevent light piping.
To keep the sandwich together, you can temporarily tape the two sheets of glass together at two or more points along opposite edges. This might sound crude, and it isn’t as convenient as a commercial glass carrier, but it works. I did this with a Beseler 23CII enlarger until I found a glass carrier. The prints made with the homemade carrier were uniformly focused and have the same quality as those I later made with the Beseler glass carrier. In the meanwhile, you can keep checking potential sources, such as eBay for a reasonably priced glass carrier for your enlarger.