Maybe you could use an inexpensive stainless steel flask (the kind used for sneaking drinks during boring family functions)? As long as it's got some sort of silicone seal, it should be leakproof and crushproof. It might be hard to clean, but if you only used it for oil, it might not be an issue. If you're hiking in the mountains and you'll be doing some significant altitude changes, you might need to stop every few hours to "burp" any airtight container to release any pressure from expanding headspace to prevent leaking.