You can get the Lumens Factory 3.7v incandescent lamp from lighthound.com. Very reputable company, I've dealt with them many times. :thumbsup: FYI, they claim 190 lumens from this lamp so it should be at least as bright as your P61, but rechargeable. Free lumens! Oh hey, if you go this route, just MAKE SURE not to accidentally put in 2 cr123's in behind this lamp, because 6v will likely fry the bulb.
As for the LED options, go to the LED section and there is a link stickied at the top regarding P60 sized drop-ins. The most popular ones are from Bugout Gear, Malkoff Devices, and Dereelight but there are lots of choices. Even "bargain" units at $12 shipped, although their quality is sometimes questionable. Regardless, all of them throw much farther than my P61 ever did! Note that most of these beams are designed for strong throw with good spill, and to me don't seem to have quite as much wide flood as my P60 and P61 does. I guess it's a bit of a tradeoff.