I own a 99 but, I'll throw in my two cents anyway. If the stock design continually has issues, you could try a set of aftermarket lenses from ebay. Perhaps a set like these, for example.
4pc Black 1993 1997 Ford Ranger Headlights Corner Turn Signal Lamps Left Right | eBay
Although I cannot say one way or the other, but a plausible theory to think about. OEM style headlights are manufactured within a close tolerance to original equipment specs and whatnot so they look identical to an original motorcraft part. In contrast, aftermarket parks that throw the oem look in the trash are built to fit the vehicle, not necessarily those same tolerances, and therefor the same faults that cause them to leak.
However, if this isn't what you want, here's an alternative. Find a set of oem lights like you want, then go to the hardware store and get some caulking or silicone of your desired color. Clear would be best. Run that around the crack between the lens and the body of the light, smushing it in good, and that should help to seal the lamp. Optionally, you could also caulk behind the gasket for the lightbulb as well without actually getting any on the glass to prevent leaks.