Dan, this will come off - take a bit of work, but it'll come off!
First, mask around the area where the paint is you want to remove, leaving a space around the paint. This is to ensure the other painted areas aren't cleaned off too!
If you're using acrylics, then use a cotton bud, soaked in acrylic thinners, and wipe the area of paint, at the same time using a cocktail stick to lift any edges that might appear.
If you're using enamels, then use lighter fluid, or enamel thinners, and do the same. You'll probably have to use the cocktail stick more vigourously with this.Don't worry about any small scratches, as you might have to very lightly sand over the area, using either very worn, and wet, fine wet and dry, or a 'Scotchbrite' pad or similar.
Either method should leave a dull area, possibly with some traces of paint still apparent.
Now, get a soft cloth, and polish the area with toothpaste, or preferably 'T-Cut', or whatever it's called in the 'States. This is car body colour restorer. If you can't get this, then use metal polish, but sparingly, as it may make clear plastic brittle.
Once done, clean off any excess paste/restorer/polish, and polsih with a soft, dry cloth. Then, give it a coat of 'Future', by brush if it's easier, and stand the canopy, bottom down, on it's bottom frame, to allow the 'Future' to settle out evenly. Do this by palcing ona soft, lint-free cloth or, second choice, kitchen tissue. NOT toilet tissue, as this has paper dust which will adhere. The cloth/tissue will absorb any excess 'Future', but if there are any small 'globs' when dry, these with lift off by carefully removing with the edge of a new scalpel blade.
This should work mate, as I've made the same b*lls up myself in the past, and got away with it!