That's one of the things I'm planning for my new machine. I did some looking around and I'm thinking of using acrylic to make the reservoir. I'm thinking of making the res 12cm wide and 6-8cm high to fit in two drive bays.
I wanted to know where I can get large, hollow cylindrical sections of acrylic. I also might make it rectangular to get the most out of the drive bay's shape. As well I wanted to know what some good glues are that would resist water or other coolants? I was thinking a two-part epoxy.