Are there stronger oxidizing agents than fluorine gas?
There are stronger oxidization agents than fluorine gas. I can name two in particular. But I don't think either would actually oxidize fluorine gas in it's pure state, for obvious reasons that you'll see shortly.

Dioxygen Difluoride. Affectionately named 'FOOF'. This is an extremely, extremely potent oxidizer. It also lights ice on fire. In fact, it lights essentially everything on fire or blows up on contact with said things.

Chlorine Trifluoride. Arguably, worse. This gas burns through practically everything, except for a few specific structural metals, but only because these form a very thin passivization layer. If this scratches, the tank burns. A notable incident with this gas, a 900kg spill of it burnt through 30cm of concrete, then 90cm of gravel underneath that concrete. It burnt over a meter into the ground.

As a foreword: I have no idea why you'd want to get within three miles of these things. Please don't light yourself on fire. It's not fun. (Trust me).