Once when I was doing research abroad, shooting microfilm for my research, and didn't have a bulk loader, I would just mark the length with two pieces of masking tape in the bathroom, and I could measure out 36-exposure lengths quickly that way.
In addition to that or swapping the Tri-X out of your bulk loader, you could just buy another one. Second hand they are pretty cheap these days, and even new ones aren't that costly. There are some people who keep three or four of them going at a time.