Yes, Arbor Fab will make a spider with any size mesh up 1520 micron. However, there is an upcharge. I do not know who thought 300 and 400 micron were a good mesh size for pellets, but that person was clearly not a brewer. One does not need to hold back the powder. One needs to hold back the larger particulate matter.
I use hop bags. I have a Blichmann plate cooler and I don’t want it to clog. But as many brewers have stated, you’ll have to adjust your hop utilization factor just a bit. Cleanup is easy; just toss it in the trash!!
I’ve been using hop bags with my plate cooler for roughly 7 years and about 80 batches with no issues.
From what I can find 300, 400, 800 are readily available, with 300 being by far the most used.
Here is a 800 micron.