If you haven't found one yet, then I think you've left it a little late for this season. You shouldn't be advertising for a stud anyway. A decent stud dog owner will not answer such an advert. As the bitch's owner you have the choice of stud and I'm sure you will want the best and most compatible with your bitch. This will take time and research. I would suggest as a starting point you contact the breed club, details of which can be found at the bottom of the KC breed standard page of their website.

PS - I don't know what health tests bichons require, but assuming you have health tested your bitch it is important to ensure the stud dog is tested too.