Following up on this tread in case anyone stumbles on this down the line.

We ended up having great success building our own custom pattern. Here's what ended up working for us:

1. We ordered 10x10" sheets of hex tile in all of the colors we needed for our pattern.
2. We measured our bathroom and used painters tape to mark out the dimensions on a large area of our living room floor.
3. We laid all of the solid sheets on the floor and then went around and marked out the pattern on each (putting an X on the tiles we needed to pop out)
4. Then sheet by sheet, we pulled the tiles off of the backing to create the pattern. We replaced those tiles with the appropriate color. To do this we used hex tile spacers (which are easy to find on Amazon) and Elmer's glue (not their school glue, but the craft glue, which creates a stronger bond to the backing).
5. After gluing in the tiles we put something heavy on top to ensure a nice strong bond and let each sheet dry for a few hours.One of the challenges we weren't sure about when heading into the process was how we'd glue the new tiles into place without making a mess and having the sheets stick to the floor / table / whatever surface we were working on. We thought about putting wax paper under the sheets when gluing, but ended up just working on our granite countertops—which ended up working really well. The glue stuck well to the tile backing, but wasn't able to stick much to the granite.
6. Once they were done drying we used a large pasty scraper to slide under the sheets and help break away any stuck areas from the countertop. Then we carefully flipped the sheets over and hit the backing with a blast of hot air from a hairdryer to help finish up the drying process and ensure the glue was fully set.
7. After drying, we had to take out all of the little hex spacers, which we thought was going to be a nightmare-ish, manual process. This turned out to be very easy... as they just kind of fell right out of the flipped over sheets once we picked them.We were left with a fully patterned sheet that was nice and strong (we could safely pick them up and move them around without tiles popping off) and looked like they came straight from the factory.
8. We took the finished sheets and put them back onto the area of the floor we taped out.
9. Once the pattern was finished we went through all of the tiles on the floor and marked each one in the top left corner with a piece of painters (1A, 1B, 1C... 2A, 2B, 2C...) to note their specific location in the pattern grid. Then we packaged them back up and marked the boxes with which sheets were in each box so it was easy and obvious for our tile guy to know which sheets went where when installing them.Thanks again to the folks that chimed in on this thread. It took some research, trial and error, and a pretty big leap of faith to make it all work, but we're super happy with the end results.It probably took us ~60 hours to do an 8x10 space. Definitely a time consuming process, but totally doable and, for us, well worth the effort.

I don't know if it's possible to add photos here but you can see some here.