You can actually sometimes find an EE-3 resin cast online. But if you want to make it from scratch, I recommend trying to find something with relatively the same style handgrip. Then everything else is just a matter of PVC piping and plastic pieces. So not all that complicated, if you know what you're doing.
As far as plexiglass for the armor plates, I would really recommend Sintra or some other form of plastic over it, because plexiglass is not very easy to mold into the shapes you'll need, and it doesn't take paint very well at all. Sintra is a bit expensive, but all you need is heat to mold it.
“What do you mean the Slave I took off with Master Fadir?!” - Luke Skywalker, Noncanon source.