I have one of the cheap nickle-plated tips from GP and it works just fine. The hole through the middle is tapered, so it's wide at the top but smaller and centered directly over the bridge at the bottom. My only problem with them is that at 5V, they get uncomfortably hot if you're chain vaping. I've solved the issue by cutting the end out of a silicone carto condom and sticking it over the DT. Works well at keeping it from burning my lips. Perhaps there's a market for a silicone-coated metal drip tip.
Or you could do away with the metal completely. Mold the whole thing out of high-temp silicone for pennies a piece. It doesn't melt, doesn't add a weird metallic taste, and doesn't get hot. You wouldn't need an o-ring because you could just mold a "bump" into the silicone itself. You could sell them four for a dollar and still make money. If I knew the first thing about moldmaking, I'd do it myself.
Or you could do away with the metal completely. Mold the whole thing out of high-temp silicone for pennies a piece. It doesn't melt, doesn't add a weird metallic taste, and doesn't get hot. You wouldn't need an o-ring because you could just mold a "bump" into the silicone itself. You could sell them four for a dollar and still make money. If I knew the first thing about moldmaking, I'd do it myself.