Cover for CP16 on trailer

[federalist]

I am looking for a sunbrella-type cover for my CP16/1.  She is stored on a trailer and the mast and boom are stowed under the hull so a fitted cover will work.  Hopefully, someone has a fix that does not require spending hundreds on a custom cover.  I just used Poli-Glow and she is looking fine and I would like to keep her that way.  I have used plastic tarps from Harbor Freight, but the sun breaks them down after 6 months and they look like hell.

Any ideas?

[KPL]

Wally world & Northern tool have boat covers fairly cheap.  They might fit.  If not, save the box and return it.  They are some type of silver fabric with an elastic border.  I'm not sure how durable they are (you get what you pay for to some extent).
http://www.walmart.com/catalog/product.do?product_id=2508678&sourceid=1500000000000003260410&ci_src=14110944&ci_sku=2508678
http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_507938_507938