Closest would be Hopewell Super Buy Rite (formerly Circle Liquors) in Pennington, on the Rt. 31 Circle. Cross the Delaware and check out Cold Spring Beverages in Newton, PA or the bottle shop at the Candlewyck Bar in Buckingham, PA.
To add on to that, Joe Canal's in Lawrenceville isn't too far from Titusville. If you are looking for a bar/restaurant to get drinks I'd recommend Vault in Yardley (awesome pizzas), Brick Farm Tavern in Hopewell for Troon Brewing (upscale restaurant, but GREAT beer) or Isaac Newtown's in Newtown.
I live in Titusville. Hopewell Buy-rite is for sure your best local bet. Troon is 10-15 minutes away for releases. And it’s worth your time to cross that tiny ass bridge without hitting anyone and drive 15 minutes to Trenton Road Takeout. Follow them on FB because they get a lot of great beers that they take online reserves for.