Mark,
I used to fly quite a bit (long-haul) since 2006 but as I have taken up permanently DE shaving only beginning of 2010, I cannot comment yet on carrying onboard a DE razor.
However, as I am getting myself ready for a three plus week trip next month, I was also wondering on what to take with me. Creams, soaps, ASs, etc. are the easy stuff - samples or small bottles should be fine. The issue is with the razor. I have decided I will not take the razor with me onboard (in my toiletries pouch), instead I will put it in the check-in luggage along with a few blades.
A general caution on travelling (not that you are not aware of it), now that we are into the subject: nice and expensive checked-in bags always attract attention and are therefore pretty often targetted in specific airports (examples include connecting airports in Italy, Ukraine, Philippines, etc.) Mind your watch, as well, if security personnel (in selected airports) ask you to take it off before going through that metal detector. I have read of an instance when one person took his (expensive) watch off as requested, watch went into the plastic tray into which we all put our laptops, only not to find it later after going through the X-Ray scanner. Never trust anyone and never believe anyone.
I cannot give any comment on DE blades availability in other locations. I lived for 4 years in Asia (and coming and going to Europe and the U.S.) but was using my Merkur blades pretty infrequently so never looked for similar stuff. Now I will, though, but to be honest I don't really expect to find much where I'm heading to this time.