you can actually source more current my connecting a transistor in series
with the output from the lm555. If you know the amount of current that you
want it to source, you will divide that by the Hfe or beta(gain constant) of
the transistor. This will tell you the amount of current that you will need
at the base of the transistor. then you take the ouput voltage of the lm555
(which should be close to your Vcc) and divide by the base current. Then you
will connect led volatge source to your led and then the led to the
collector of the bjt. Hook the emmitter to ground. This way when the output
from the lm555 goes high, the transistor opens allowing the current to flow
from the led voltage source to ground. Which will allow the led to light. If
you want to change brightness let's say from bright to dim then you would
hook up a pnp in parallel with the afformentioned npn. Then set the amount
of current that you would want it to sink similar to the way mentioned
above. That way it is bright for part of the duty cycle and dimmer for the
other part.

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