How about coming up with some off the shelf or homemade diffuser of
some kind to snap or attach to the end of the 1157 LED bulbs? Sure it
would take more than just spraying some white paint over them but
doesn't seem insurmountable... some thick white transluscent plastic
lens, clear plastic lens with bunch of metal flakes suspended in it,
little piece of foil on tips of the lenses and them white material at
base fo lens so light bounces off the lens back onto the white backing,
I dunno. How bout just clear lens that spreads the light out like a
projector? Maybe once you diffused them perfectly then you'd find out
they don't have enough light output anyway.