Oh no. How stressful for you.
Is it possible to bring in a bowl yourself (f they have nothing for you) and just transfer the sample to the cup? I would think they should have bowl there. I remember when I had a 24 hour urine collection test and they gave me a bowl that fit over the toilet but under the seat, so I could go normally and still collect everything. They should have something, or maybe a medical supply store would have something you could take there?
Good luck. I hope it works out.