There are also the AquaC Remoras. They have one that is designed for nanos, can't remember the model.
Generally with a hooded nano, you are going to need to do some modding to make a skimmer fit.
Those little fit-in skimmers that are designed to squeeze into the filter compartment like the Fission skimmers are total bull plop, don't waste your money or sanity.
I just said the heck with it on mine and took the hood completely off, then added a eshoppes overflow and sump where I have a recirculating skimmer sitting in the bottom.