Will you be storing it where someone will see if it doesn't match? If not, I encourage you to get a cheap "spare" rim of the proper size with a tire the same as your others. If it doesn't match, it will only bug you that much more to get the original tire fixed so you can get that cheap spare rim off of your pretty trailer.
Otherwise, you will probably either have to go to Tracker, or post a picture of your rims on several websites in order to get a perfect match. I'm not certain that the rims on the 2005 trailers were "standard" items. Maybe they were. Maybe not. Pictures would certainly help.
All the best,
Glenn