Resistor - Correct value for optocoupler, but dont have that size
1kΩ will be just fine. But if you want lower you could take two 1kΩ and place them in parallel - that will give you 500Ω.
BTW - 1kΩ will give you ((5-1.3)/1000=) 3.7mA through the diode of the optocoupler, and 500Ω will give you ((5-1.3)/500=) 7.4mA.