I posted about this once before. I would say there can be a place for tethers, but not where you suggested. Breathing is one place you must be moving forward to do correctly. Otherwise, you will not be creating the bow wave you need to find the correct amount of rotation. Balance will be tricky because most tethers can affect your balance some. I can see using the tether to work on timing, rails, relaxed recovery, patient catch, kick timing, etc. The added resistance of the tether might even increase the firing of your nerve circuits and imprint the correct action more quickly. But you must be extra careful to be doing it right.
I don't know of any that won't limit rotation at least a bit. The single cord styles such as Stretch Cordz - short cord slider would probably be the best.
The thing I like doing best in a short pool is being really picky about the basics. Just how slowly can you kick and still maintain balance? Just how straight can you get your body in skate? Just how easily can you hold that skate?
The other thing I think might work is to plan your training around your trips. Can you use the trips to do more drill work on new focal points, then return home to try to incorporate those into your full stroke? Can you find hotels that have lap pools?