Don't waste your time with the AA/D converters (I know, I tried them in my Herc 350) - the hercs draw a lot of power due to the internal cooling fan and the life of the AA's is minutes at best.
I tried some of the Juice brand rechargeable D's and was disappointed too - they have an OK lifespan but they charge up at 1.2-1.3v so your power will suffer, I've been looking for some 1.5v rechargeable D's myself but almost all are 1.2v (even though some of them will recharge to 1.6v they dropoff so fast from what I've read on other forums,etc that they just aren't worth it) ...
Right now I'm just buying Energizers in bulk from a local security distributor (they sell discounted bulkpacks for security guards who use them in their Maglites, etc) - 24 of them runs me (IIRC) like $17 so you might want to poke around locally and see if you can find a similar deal (shipping from just about anywhere is a killer due to the size and weight of the batteries).
As to accessories, Email Laserglow (Justin) and he'll send you a list of what's available, some of the accessories, parts, etc aren't listed on their site (extra keys, plugs, etc) - They sell the x10dr expander for $439 ($289 if you are the original purchaser of your hercules and can provide original order date and sn#) here:
http://www.laserglow.com/index.php?x10dr - another pretty cool toy I have is the final lens assembly from an American DJ Topaz stage lighting fixture (see pic), you can but the older Topaz lights on fleabay for like $50 (or less if they aren't working) and removing the final lens is a snap, it's within about 2mm of the hercs diameter and actually looks like it was made for it, it gives you an incredibly expanded "flood" beam (think 150ft green circle on low-lying clouds, 8ft green circle at 250ft, etc) and while the optics are far from "laser quality" it's a lot of fun that doesn't look hokey for well under $50 if you're lucky!
And finally, most importantly, GET SOME EYE PROTECTION, the herc (even the little ones) can cause permanent, immediate damage (some not readily noticeable) even when reflected, watching the burning spot, etc ...
