Joe, the Honda valve has been unattainable for several years. It is not special enough to waste time trying to find one. I have not been very active in the parts scene as of late but to my knowledge, someone had a repair kit for the valves. But I do not know who. Also, MGB uses the same valve internals although the valve exterior is different. There are plenty of sellers of MGB valves. If you are a natural Macgyver, you can transfer the internals parts. Learn by taking yours apart. It is no good anyway.
Hopefully someone will know where to buy a kit. If you don’t care for originality, your local NAPA or any parts dealer can provide a general purpose valve quite economically that works great. Just look at their pictures of valves and pick one with the features you want, like 1/2″ in /out and a lever that operates in the direction you want it to close.