There are several guys-friendly dates to go out on. You can even ask him to a concert or group date which makes it much more fun and distracts him from thinking too much about what motivated you to do that.
There are many other strategies you can use to ask a guy out in a date without looking cheap. You can ask him out over the phone or even put a simple note on his desk. Never let him see you nervous or doubtful in a way that will make turning you down seem obviously hurtful. Walk up to him in the presence of his friends to help you out with this.