The collapsible mast like everything else I made myself. At a local metal supply I bought a 6 ft. piece of 3/4" blue anodized tubing. Also a length of 5/8" tubing. The 3/4" I cut in 12" sections. The 5/8" in 5" sections.
The two sizes are pretty much a precission fit. One slides inside the other for a good snug fit. To keep one side from falling out I simply and lightly tapped one end of the 5/8" with a small rubber tipped mallot. The now out of round end is pressed inside the 3/4" and stays put. You can add shock cord but this makes it easier to use just what you want.
Here is my settup layed out next to the topbox on my project table. After seeing 5 ft. is more than enough I use the 6th piece for a camera mount. The other piece is the adapter for the umbella and mast. The adapter was needed to raise the unbrella up just enough for proper height over the bike. I use only as many sections needed over the bike and have a reach of 9' total. The unused sections of mast are used with my paper towel holder and supports a small lantern or pushes the tarp up higher over the table as needed.
Stowed size is 14 1/2" long and fit easily with room to spare in either side or topbox.
Total cost was around $12. The bag for storage is an extra tent pole bag I had laying around and the camera mount was broken and found at a local garage sale.
And the tarp, it really isn't a tarp at all. Its a Footprint for REI's Hobitat 6. Looking at both I noticed how much better the footprint was made right down to the sewn on nylon straps at each courner with D-rings. Also blocks out more light for better shade and only cost $5 more then the tarp I was looking at. If it ever fails REI has a great return policy.