While you will not run across it normally while walking around the Hisuian region in Pokémon Legends: Arceus, you can encounter the original Johtonian version of Sneasel in space-time distortions. This form will not evolve into Pokémon Legends: Arceus’ new form Sneasler. Instead, here is how to evolve Johtonian Sneasel into Weavile.
Evolving Johtonian Sneasel into Weavile in Pokémon Legends: Arceus is very similar to making the Hisuian Sneasel a Sneasler. All you need to do is give it a Razor Claw, but specifically, it needs to have it at night time. Doing it during the day will not have any effect, unlike the Hisuian form.
To get a Razor Claw, you can purchase one from the Trading Post in Jubilife Village for 1,400 Merit Points. To accumulate Merit Points, you will need to find Satchels out in the wild that are dropped by other trainers who have been knocked out. If their Satchel has more items in it, you can turn it in for a sum of Merit Points.
Additionally, you can potentially encounter a Razor Claw while riding a Ursaluna. When on them, follow their indications, and they can dig up rare items, including any of the evolution stones. If you want to waste some time, this may be a good way to load up on hard-to-get objects.