Most of the P.A.F. style bobbins are pretty close in bobbin height, but do vary a little bit from manufacturer to manufacturer and even by material. But with your pedigree & background, I am sure you know this already. Do you need both slug and screw bobbins & what color(s)? I will check my oddball drawer to see what I might have that will help. I'll try to check tomorrow.
Have you considered going with a 42.5 gauge to give you the extra room for a higher TPL count? Maybe even try single build insulation wire...not sure what type of insulation and wire you are using for this project (42...single, heavy, or triple).