Hi
@davisgirl ........Two ways you might could go about this............check in housewares or ask somebody in Loew's or whatever store you have in your area........for closet rod hanger rods.....check and see if they have anything that might work here....some of the methods they have for attaching the hanger rod in closet......I've seen clamp on and screw on types.....see if one the methods there might work...you'll have to adapt it somewhat, but it shouldn't be very hard.
The other method would involve using PVC plumbing pipe and T joints............you could split the joints and glue them over your poles in your tent and then fit whatever length you need to span your tent. These things would not be as hard to do as they may sound.
Another thought just came to me.........you could try electric clamp on fixtures like the ones we[growers]use when using some kinds of CFB lighting. You would clamp the fixtures on the back and front poles and run a piece of PVC pipe or and dowel rod between them for your cross piece. Hope this helps! if I can help further or you have a question, just send me a PM.