I’m very sorry to hear that you lost your male, sir, but you should have no difficulty replacing it with another fine Mustang stallion.
Just place your order for a single (1) Mustang and then use the "Comments" section of the order form to specify that the seahorse must be a male. The "Comments" section on the online order form is for any such special instructions you may have regarding your order, such as delivering the seahorses on a specific date. That is the place where you can request seahorses with special traits when you place your order, such as the gender of the seahorse. State that you need a stallion to replace the mate for your female Mustang, and that you will accept only a male Mustang. Ask them to cancel your order and to telephone you if they cannot provide a suitable male Mustang for any reason at the time you placed your order, Ken.
Given a choice, Ocean Rider always tries to place their seahorses with knowledgeable hobbyists who are the best prepared to provide them with good care. So be sure to mention that you are an experienced seahorse keeper and a repeat customer who has ordered Mustangs from Ocean Rider before and always enjoyed good success with them.
Best of luck finding a new mate for your lonely female, Ken! Here’s hoping that she hits it off right away with the new Mustang stallion and that they settle down and set up housekeeping very soon.