Are these steel wheels? if it's in your budget you could pick up a new (cheap) wheelset with an actual track hub for around $120.

the problem with these threads is that we don't really know what you mean by wanting to keep it cheap. It would be nice to know what you mean by this, as in 'I want to spend $50' or, 'I want to spend $25' or whatever.
It'd also be helpful if we knew what kind of RL help and tools you might have access to. For example, if you were my neighbor, you would come over and we'd take off your freewheel and try to thread a track cog on, answering several questions in about 10 minutes.
Your best bet is to find a local fixed bike nerd and give him a 12 pack to spend a few hours with you and your bike. Anyone in Chicago want to step up?