We sure do have an inline female plug. We have them in green or white and in SPT1 or SPT2. You can find them here: http://www.thechristmaslightemporium.com/lights/christmas-light-installation-accessories/slide-on-vampire-plugs/?v=7516fd43adaa
In a pinch, the standard female plugs can also be modified to be inline. Sometimes folks use a pair of cutters/dikes to snip a notch in the closed end of a standard female slide on in order to use it as an inline plug. You have to be a little careful if you do that as it’s somewhat easy to crack the plastic while cutting. Our install teams do this white often. But the standard inline plug is a much easy, better, safer way to go.
