Dave,
I use standard plumbing PVC pipe available at Lowe's or Home Depot.  
Installing them requires unscrewing the stays and drilling a hole in the cap  peace 
for the end of the stay to fit into. Total cost is around $6.00 and they  last 
for several seasons. I have thought about painting them prior to installing  to 
make them last longer, but have never done it. If my rum soaked mind  
remembers correctly, they are one inch PVC pipe. Perhaps someone else on the  list 
can help here.
 
Rummy