K, so it sounds like you need one of those party lights with the silk like what I found here via Google Images.
HauntedProps:
Lighting / Sound / Effects / Illusions - Blacklights / Strobe Lights / Haunted Flames / Lighting Effects
They make them in different sizes and configurations. I had my old high school buy one that was in a box approximately 8x12 and it looked really good in a fireplace
unit. I'm sure it would also look really good if you surrounded one by faux rocks. Seems like we paid about $40 for ours (the prices seem high at hauntedprops.com). We got ours at cheaplights:
DJ Equipment | DJ Lights | Fog Fluid |Stage Lighting | Chauvet lighting | DJ Gear, but they no longer offer the model we got. Looks like they only have the large format
effect. You might give them a
call, or search other DJ lighting retailers. The keywords I would use would be along the lines of flame
effect light, fire
effect light, flamer light (be careful with that one lol),
etc.
Here's some clean results I found by Googling "flamer
effect". First result. The prices seem more reasonable.
Party Lights Online:
Flame lights have the illusion of real flames and are safe for indoor use.
They're still not ideal, but it says you can use the first one as a standing cauldron, which would fit your use if properly masked. It takes batteries though. The second one operates off 110v., but mentions no self-standing abilities, I'm sure you could make it work.
I bought some of the mini-flame wall mount lights once for a production of Peter Pan and though cheap, they look realistic. They got great responses from the audience every night. Though not recommended because of the fan motor and possible
transformer inside,I've dimmed these many times with no problems (in my younger, more foolish days).
This is how they work:
A fan blows upward on a piece of white silk (usually about 8" wide and 8" tall cut in the shape of a flame. Three MR-11 lamps with colored lenses aim up at the blowing silk. The one in the middle is usually colored blue, and the sides are orange.
We have a member here on CB known as BillESC. He is an Authorized Dealer and usually able to get a hold of these more obscure lighting effects. You might
send him a PM.
Here's one more google hit.
http://www.littlebrightlights.com/site/1435548/page/610933. Scroll down to the bottom of the
page to see some replacement lamps and silk.
Hope this helps.