Rope Halters
The rope halter is my favorite of all training equipment.  However, they're expensive, anywhere from $50 to around $25.  I've found it's less expensive to make them (not a difficult discovery). So, I pass the savings to you. 
foal/weanling or horse halter - $10
oversized/warmblood hlaters - $12
(plus shipping if you don't come get them).

Contact for details