Based on pezmc's email version. Same trigger search and action message, just changed method from email to alert.
If
New post from search
This Trigger fires every time a new post submitted on reddit matches a search query you specify. NOTE: limited to 20 items per check.
Then
Send a notification from the IFTTT app
This action will send a notification to your devices from the IFTTT app.
ID tvJeMcgR
Explore more great ways to automate Notifications and reddit