Decent wireless cans are not cheap. What you are after is
these.
You see, most 'radios' people use are half-duplex. That means that you either talk, or you listen. You cannot do both. This sort of technology is not overly expensive. However, what we need as SMs is called full-duplex, which I am sure you can guess, is two way. You can talk and listen and it costs more than twice the price. There is a very simple reason why full-duplex is considered a 'necessity' in most theatres, and that is safety. Being a student at a school that may not matter too much to you as chances are you will have a teacher on hand to deal with those sorts of things. If you are really worried about needing to move great distances, get yourself a REALLY long mic lead - clearcom/telex/techpro compatible cans systems all use your standard 3 pin XLR cables. You can buy 20M for about (AU)$25 or so.
a 20m cable will give you more than enough freedom. The rest is learning cable management. For example, don't walk one way past a table then come back the other side. Get used to trailing a hand behind you to pull the cord along or you can do what I do, which is to use LX tape to tape a ring about 40cm down the mic cable, then use a small carabina through that ring and my back belt loop to put the strain on my pants instead of on the belt pack and connection (the cable lasts longer).
You will learn little tricks the more stage management you do to make your life a bit easier.
However in response to your orrigional question. Yes, you can buy a single wireless can station that will interface with your telex system. However I doubt you could afford it.
