Are you going to race on a ploughed track or do you want them for winter riding in general? A tire built for clear ice will give you fantastic traction but turns into a banana peel as soon as you hit some snow. I know a few guys who race and may have some used tires. Most ice race tires are also usually shaved to create more of a contact patch when leaned over on counterclockwise ovals, and are not studded on the right hand side, so if you want to turn left you may need to build one. They do build them for ice road race circuits non planed and studded on both sides, but they may not be as easy to get. It's not hard to build a set of tires, it just takes a bit of time. A new set of competetive ice race tires will run $600-$700.
Clean ice tires look like this
and multi purpose snow and ice tires look like this