I use one of those leadlined bags from... Tenba or Tamrac (or something else) I think but got it long time ago and dont notice which brand. Only problem I have is that when it goes thru the xray it looks like you're concealing something, so 8 out of 10, the security guy will ask you to see it... if that's the case you might as well let them hand inspect the film. That's what I thought at first, but once I had 20 rolls of new film at KLIA and the lady officer wanted me to open every single can of film roll to make sure its film inside!!!
So, either you pass it turn in a xray proof bag, or hand inspect them with the box removed for ease, or be like me now... I dont care too much anymore, most of my film goes thru the xray machine (I use mostly Kodak 400TX and Ilford FP4+). I guess compared to the check-in xray, the handcarry xray machines are not that powerful. Anyways, if you're paranoid about the x-ray machines, I was told that when the ship the film to you, it was probably scanned at one point or another during importation into Singapore, so....