While I agree, this is difficult to do. Quality soaps/creams are difficult enough to find, let alone find in travel sizes (which would only further the costs as well). My only suggestion for this is to buy the small reusable plastic travel containers that are under the TSA's fluid ounce rule. Filling these with shaving cream can be difficult though. For all the hassle, it's probably worth it to just buy a cartridge razor and travel size bottle of Barbasol. If you travel often however, you may be SOL. Hard soaps though would probably pass the TSA check though.
This sounds like an argument for a decent quality but low viscosity cream like Kiss My Face. It would be fairly easy to pump into a travel bottle, and decant from same.