Unfortunately I don't believe that is big enough to sustain a
pod population. Scooters are as hard to keep as mandarins, imo, and shouldn't be kept in anything but large tanks with a lots of live rock for pods to thrive in.
I think you have a couple of choices, none of which is going to make you happy:
1. You can order pods online, but they are about $30 and my guess is you would have to purchase them at least a few times a month to keep your scooter alive.
2. Take him back to the LFS...perhaps they can put him in a tank where he can survive. Perhaps he will get lucky and be sold to someone with a large tank with a big pod population. Or do you know someone with a tank that fits this description?
3. Purchase a bigger tank yourself.

The only problem would be curing LR...that normally takes months.
4. I was going to suggest a pod refugium for your tank, but I think 12 gallons is just too small. Perhaps not...and others will chime in.
Sorry to sound so gloomy!