Since you already have the E2L and E1B, the first and cheapest solution that comes to mind is the SureFire F04 beam filter. It's a handy little diffuser that fits over the head of any SF E-series light, and spreads that tight TIR beam out into a very usable flood. I've got one for my L1, and it works wonders, both on the L1's low setting for close-up tasks, and on high, when I need to light up a room. And at $12, I doubt you'll find anything better or more convenient.
If you're looking to get a new light, though, you've got a number of options. As has been stated, the L4 and U2 are among the options available to you. The L2 would be another; as far as I know, it's beam is pretty close to that of the L4, but it gives you 2 levels of light. Personally, I'd say that the G2L (or 6PL) would be more economical, though. With that, you get a relatively tight hotspot (good for some mid-range throw, as well as focusing your vision at a single point when searching or investigating something), and a spill beam that is plenty bright and usable. Not having the L4 et al, I can't make that comparison, but my G2L has great spill; much more usable indoors than my L1 without the diffuser (outdoors I prefer the L1's beam, though).
As has also been mentioned, you could get a G2/6P and put a Malkoff M60LF (or M60F, as long as it's in a metal body) in it. This gives you a great beam, perfectly smooth with no rings whatsoever, and no harsh transition from spill to no light, as you get with reflector lights like the stock G2L. The M60LF also gives you a pretty good amount of throw, for a flood light.
The best flood light I've used, though, is a SF C2 with Malkoff M60 with a SF FM34 diffuser. Like the F04 for the E-series, the FM34 fits on the C2/6P/G2/etc., except it diffuses the beam even more. The beam you get is much more floody than the M60LF would give you alone. You don't get a lot of throw with this filter on, but the nice thing about it is you can flip it to an "off" position whenever you want, effectively giving you a light that lets you choose between spot and flood. Here's a beamshot comparison to demonstrate:
Mind you the FM34 can be used on any 6P-sized light, and you could keep the SF P60L if you wanted. I do recommend a Malkoff M60 or M60L, or some other bright drop-in, as the SF module doesn't have the greatest efficiency.