During the winter squats could help, if you can keep a bar in the office, no problem at lunch time for example three times a week. Like 3 series of 15 reps for example at a reasonable weight, for cycling you need more fast repetitions than too heavy of a weight. During spring and summer install a bike trainer on the office and do 30 minutes (if you have access to a changing room and a shower) just to keep your legs going and to avoid losing your fitness level. Explain to your collegues, who might see you doing this, how fast an athlete can lose condition, they will still think you are crazy but at least they will leave you alone,