Home made matt board option
For odd ball film sizes smaller than say 6x7, for which I do not have a 'factory' neg holder, I carefully trace the pattern required for the neg holder onto 2 pieces of 4 ply matt board (start with black, or be prepared to use lots of sharpie marker to turn it black). I then find the center, cut the required window, hing them with tape, and I am away to the races. Use sharp xacto/snap off knives, and swap blades frequently; this work dulls them quickly. I have a stock of these units for when I am called on to print 110, 126 , and 127 older negatives.