A simple plastic enclosure should work just fine to protect the NEO-M8P. Depending on what you have the GPS breakout connected to (eg. microcontroller, single-board computer, PC etc.), you’ll need to have holes in it to run those connections to the device and also you’ll need a hole for the antenna wire. Most adapter cables like this [RP-SM to u.Fl have a lock nut so you can mount it easily on something like your enclosure. Just make sure to do your best to seal any openings that might have moisture/dust/debris get in. You can either use something like a rubber grommet or if you want something more permanent you can use some conformal coating or another water-proof sealant on them.
As for a specific enclosure, the right one would depend on what you are connecting the NEO-M8P breakout to. You can browse through all of the enclosures we carry [here. While not specifically related to the GPS breakout, [this tutorial for a weather station has some tips for protecting your electronics from the elements.