After asking a similar question about a cover for my 16", I've ordered a Telegizmo from the US. Cost of shipping seems reasonable - they don't have a dealer here. A few people suggested that I try Peter Reid from sdm telescopes, but he doesn't seem to stock them and suggested that he could get one for me but it would be easier for me to get one from the source. Cost for cover for 18" scope was US$139 and shiping US$43
The relevant IIS thread is
http://www.iceinspace.com.au/forum/s...ad.php?t=51738
and is worth a look as I had some good advice.
Link to telegizmos is
http://www.telegizmos.com/index.html
Ands Scott also suggested astrosystems looking at
http://www.astrosystems.biz/covers.htm and
http://casesandcovers.com/