there is a tutorial in the UKSB demo area by Paul Davenport on creating them using acrylic. this sort of thing takes allot of time and experience to do it right.
if you are looking into investing in this line of work for trade supply and the like, it maybe better to look at purchasing one of the automated return workshops readily available now. there are various companies offering them. one i looked at about 6 or 7 years ago was the Arete Return machines… i just googled them and cant find the original site but this Australian one comes up, so will give you a starting point.
http://www.hmhaustralia.com.au/arete.html