Funny that you mention this, because I will soon be getting a sealed quartz ampoule containing a mixture of 33% F2 and 67% He. I got it from the site
http://www.elemente.at.cx/. The payment went through today, and he will get in touch with me as soon as it ships. (I also picked up some unoxidized, ampouled sodium and some amorphous red selenium). According to the discussions I've had with the owner of the site, the quartz ampoules have been specifically treated to remove the -OH end caps and metal contamination that generally leads to the decomposition via fluorine gas. The F2 has also been completely dried and diluted with the helium gas to prevent it from attacking the quartz. He's had samples sealed up for quite some time now and says that there are no signs of damage. For only 30 Euros for a pretty large sized ampoule, it might not hurt to give that a try. Or you could perhaps talk to him about purchasing larger quantities in actual cylinders.