Followup on this thread. I just ordered a total blackout blind system with side channels, bottom channel seal and light-tight upper cassette from This is a USA company that was very easy to deal with and will be shipping all the components straight to me for only $40 postage.

The other companies mentioned either were not interested in selling their product or did not respond to my inquiry. Shy UK did respond with a nice quote but wanted me to arrange shipping from the UK, which I thought was strange, but maybe that is the way they do things across the lake.