I've had the same problem finding low-dose melatonin in brick-and-mortar stores, but Natrol sells a 1mg dissolving tablet on Amazon. If I need a sleep aid, I break it in half for a ~0.5mg dose, chew it with my front teeth, then hold it under my tongue for a bit before swallowing what's left.
It usually takes 15-30 minutes before I get noticeably drowsy, but I feel no more groggy the next day than if I slept sober.
For low dose melatonin, try liquid melatonin. Around here Sprouts carries it, but you gotta look a bit to find it. The bottle says 30 drop equal 3mg. So you can take small doses easily, and it absorbs under your tongue pretty quickly.
most bricke and mortar should have at least 1mg tablets, and you can break those in half. or break a 3mg into 3rds. not perfect but should work.