Would there be any suitable origami diagrams or designs for these?
The usual way is to use gore-tapered strips like [these] to build up a balloon using glue, or to make something similar to this:

... but I wondered if any there could be any different and considerably smaller origami designs which still work? (the one shown in the picture is about 5ft tall!)
Tissue paper would be a dead cert (low weight) for the body, with possibly a cylinder wrap of metal foil around the tealight protecting the flame from the sides.
With taking strict safety precautions, it might be a bit of fun.