Well... there are a couple of things you might be able to do. First, I'd go check for a blonde wig in one of the box stores, since they'd be on clearance.
(If not, I have a wig you might be able to use that I want to get rid of.)
Then from there, you can go to an ethnic haircare store and try to find yacky. It's fiber that looks like hair that's intended to be braided into a person's existing hair. It's cheap, and you get a lot of it for what you need it for.
Once you have it, it's a little frizzy, so you can either blow-dry it or boil it (which I've never actually tried). It tends to damage the ends, so keep that in mind when buying what you need.
Once it's straight, you can add it in either using some of the information in
this tutorial, or do what I do, which is take little pieces of interfacing, cut it into strips about an inch by two inches, spread low-temp hot glue over the surface, add the hair, and then roll the interfacing overtop, sandwiching the fibers until cool, and then trimming off the excess, then gluing it directly to the net. People cringe when I suggest this, because it's not the most elegant way of doing things, but it works well for me, and if you're careful about applying the interfacing, no one will ever know. It's also not quite as permanent as sewing, since in extreme heat, it could melt off. It's never happened to me, but I've heard it's possible for things to become unglued in summer cons. I've found that doing the wigs in the way the tutorial shows makes it hard for me to wear the wig because it reduces the space in which my head (and enormous pile of hair) can occupy.