I think the Preppys are easy to convert to eyedroppers, but I’ve not tried it. That’d probably be the cheapest way to go...
I think some folks were just using a little silicone grease to seal the threads of the body. Might be worth a shot! It’d be a pretty cheap experiment, anyhow.
I don't mind the Preppy...it has a refillable cartridge you can purchase separately.