Cat with history of urinary troubles vomiting?

My 1 1/2 year old cat has vomited twice today and is not eating/drinking water. Now he is acting pretty lethargic - under beds, sitting quietly, he normally runs all over the house and plays with everything and everybody! Normally this would not concern me as he only vomited twice, but I want to be sure. He has a history of urinary problems and is now on Royal Canin Urinary food for his multiple urinary blockages.. hasn't happened since last summer. No new food, to my knowledge he hasn't gotten into anything out of the ordinary. Any suggestions? I know everyone will say just go to the vet, but it's already 7pm and I would really rather not spend 5 hours and 400 bucks in the emergency vet. Any suggestions are welcomed. Thanks!