I've never done a Link costume, but from what I've seen, they are expensive as crap. As most other cosplay type costumes (excluding those that are in regular costume shops, such as the Mario costumes and Power Rangers, etc.).
But, what I do, is I actually do my own cosplay costumes (I'm doing Zelda from SS this Halloween). I would suggest to get the hardest part (the hat) from an online store (I think Amazon has one). Otherwise, Link is a pretty simple outfit. The undershirt will be very easy to find, just a long-sleeved shirt in that color, and I bet you can find the tunic pretty easily. What I do is, if I can find the right style/cut, but not in the right color, I get fabric dye, and buy one in a very light color. For toon Link, you'll need brown boots (or boot covers) and white pants. The belt can be made out of a basic belt, and then create the buckle, and you can just glue that onto the belt.
Another helpful part is, if you know how to sew, you can make a lot of this by going to a fabric store. I don't sew very well, so I limit that to accessories (like Zelda's shawl, for the one I'm doing; for toon Link, I don't see anything that should be too hard to find without sewing). Any designs can easily be painted on with fabric paint. And it seems like you got the equipment covered. Are you going to do the pointed ears, as well?
Hopefully I've helped, at least some. I have to say, it's good that you're planning this so early- it will give you time to find the right stuff and adjust as needed. And fortunately, for a lot of cosplays, if done right, the clothes can be reworn elsewhere, so you're not 'wasting' money for one night. Just let me know if you have any other questions, and I'll try to help!
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