HelpMe

It's also possible to catch another Espurr in the Aqua Hideout. You don't have to wait until getting Ditto to get another one.

Caught it. Thanks!

Sorry for reviving this, but this didn't quite clearly answer the question about Zangoose. I looked through all the Alleyways at night, and I still can't find Zangoose. Are there any other conditions that have to be met to find Zangoose?

Actually, you can get Headbutt even before Julia. You just have to catch a Bidoof and level it to 15. Then you trade it to the man in the house to the right of Mosswater Factory for a Litleo. Litleo will already have Headbutt as a move as it learns it at Level 11. Since Bibarel will be Level 15, you also get the bonus of Noble Roar.

I finally found one and caught it. Thanks jman390 and ~Derpy Simon.

I've been looking during the day, though it is raining for me. Is that the problem?

I'm asking this here because I've been looking where I'm supposed to when I'm supposed to. Has Sentret been moved from Obsidia Park? I've yet to encounter one in the past day.