Well, LA Reefs (.com) has them, if you are willing to wait until they are in stock again. Also, I just found this random blogspot called "Marine Farmers" that mentioned they were propagating blue ochtodes sometime last year and has a relatively recent post, so I assume they are still up and running. There is a contact form on the blog, so you could ask them if they have some.
If that doesn't work, I would try all the major reef forums, as well as the local forums for clubs your area. Nano Reefs has plenty of macro algae growers, and I don't think they have a policy about the sales forum like Reef Central does. Take a look at Reef 2 Reef and 3Reef, too. They might have members who grow this macro. Though I don't know whether or not they have a policy like Reef Central does about who gets to use the sales forums.
Lastly, try looking through people's build threads on the major reef forums, and PM the ones with (healthy looking) Blue Ochtodes to ask if they would be willing to sell you some. It might be a bit awkward, but desperate times call for desperate measures.
Also, I would love to see your tank. I am a huge fan of planted seahorse tanks! Do you have a build thread?
