I contacted Duckitt last year but am sorry to report that they did not reply; I used the
info@duckittnursies.com, perhaps the other address you found will help. I'll try to e-mail them again.
There are some domestic nurseries offering disa. Two that came up in my search are goreorchids.com and camponeorchids.com. I believe they are both in Oregon.
Very few members of our local orchid society have had success with disa. The few members that have had success claim they are as easy as cymbidiums
if you have pure water.
Are there any nurseries in your area offering disa?