...however, when I put a gel directly on the flash lens, sometimes the gel melts a little right near the area of the flash tube. I don't know how long something sticky would last.
Not here to promote any individual's business, and I do not receive any compensation of any sort for mentioning this, but since the topic is pertinent, thought I'd say that I personally bought the Demb filter holder that attaches to the flash using the velcro for the Flip-it.
The filter film is a little clumsy to remove and insert from the protective pocket, but it's still handy. He provides filters for incandescent and fluorescent lighting.