I had a similar lantern and I replaced it with a TerraLUX TLE-1F. It was just a luxeon 1 Watt led. Anyway, the lantern was negative centre so this thing didnt have reverse polarity protection and that was the end of that.
I also have a Tektite LPR-113. Its a 1 Watt luxeon with side emitting optics. Its positive at the centre but it does have reverse polarity protection.
NiteIze also has a replacement. Its a 1 Watt luxeon too.
The best I've come across is the EverLED. Its a bit pricey but its the only one I know that is regulated. Its also a 1 Watt luxeon too and it has reverse polarity protection.
Thats all the ones I've used. They are all positive at the centre so you may need to rewire some things.