It can be done, but I really don't recommend making your own filters. Based on what you're writing, you'd probably need to stop by a hardware store to buy materials for this sort of contraption.

The threading you're looking for is 40mm with a 1/7" thread pitch. How you rig the N99 or N95 particulate filter to filter it is up to you. Ultimately the level of protection it offers may be just fine, or it may be imperfect and compromised.

If you can, I'd just get a factory made P3 filter by 3M. 450-01-01 models work, and aren't to expensive (~$12, while more than they're worth, is still "reasonable" IMO). For comparison, a case of 20 of these things is $36 on amazon, but they won't be in stock until a month from now.

This filter will work, will almost certainly be more safe/professional than a jerry-rigged filter, and will function until you struggle to breathe through it since it's a particulate only filter.