Assalamu Alaikum 
When people are at work then why do they go to the toilet? Because they  have to right? Sameway we HAVE to pray Salaah no matter where we are  there are no excuses to miss it at all. No workplace or educational  institution will ever stop you from praying but most of the time you  never even have to tell them anything because it does not take long at  all.
When people go to the toilet at work or at school then they usually take  5 minutes or longer. So instead of going to the toilet then you can go  and pray which will take you even less time than a person who goes to  the toilet. It is not difficult to pray at work at all but we make it difficult for  ourselves. We can pray ANYWHERE apart from the toilet and where there is  visible impurities.There is no excuse for praying Qadha after work because there is  sufficient time and space at work in order to pray all of the Salaah. If  there is no room allocated to prayer than there will always be a room  empty. If there is no room empty then there is always a corridor,  staircase or any place where there is sufficient space in order for one  to make Sajda properly.
 
Let us be of those Muslims that when prayer time comes we  strive to pray no matter where we are and what we are doing. So let us  make the FULL effort for the pleasure of Allah and do not forget who  gives us the jobs we have and the food we eat and the very life we lead.  So let us pray to the one that is worthy of all worship.
Insha Allah Khayr