I agree with @pfm about the utility and ease of use of the Apricorn Aegis. I use that drive and Datalocker DL2 drives at work. I can’t really recommend one over the other, as they are both very convenient and effective.
To address @kieran’s concern over auditing, I can say that both drives are US DoD approved for transport of highly-classified data. Not being a subject matter expert in DoD procurement regulations, but working in cybersecurity, I don’t know that the military audited these drives, but I think it is almost certain that they have. Of course, that doesn’t mean average folks like us can audit them and your trust factor in the US DoD may vary. 
Having said that, they are not inexpensive and I don’t really have that kind of cash to burn. LUKS is good for me, but if you value, and can afford, convenience, they are both good options.