a) Perform core exercises using kettlebells if you have a gym or can take them, or hotel furniture if you can’t - chairs for tricep dips, planks, bodyweight exercises etc
b) On a gym running machine or outdoors, a daily 10k run incorporating a mid-run 10 mins of 1 min on/off “not quite sprints” or as hard as you can for a minute. I’m not a runner so there could be a proper running term for this…
Look into renting a bike. It’s not popular in American but seems to be much more prevalent in Europe. You could also pay to ship your bike directly to be without it less.