We have the iStim and have enjoyed it just fine without the Gel. However, I recently had some medical tests run and the nurse used a similar product before attaching the the little sticky pads to my chest. I asked her about the gel and she did confirm that it does improve the electrical connection. So I will pick up a tube at some point.
Eden used to carry the Fetish Fantasy Electro Sex Gel
, but it was recently discontinued. I wonder if a large drug store would carry the gel locally. If not it is available online.