All right dude-
To help answer your question this is what I did:
1: Measure the inner diameter of the pole where it's hollow. (This is important as you will need the correct measurements to purchase PVC pipe slightly smarter in diameter so that it easily fits inside the pole and can be secured with chain assembly bolts/screws.)
2: Go out and buy said PVC pipe and cut it to your desired length. (Any hardware store will do but Home depot cut it in lengths that I needed and didn't charge me any extra.) I used 4 ft. pieces because there are a lot of long holes at my course and often you can't see the basket because of elevation or foliage.
3. Check the chain assembly that rests on the top of the pole. See if there are any bolts/screws that help hold it and can be removed so that the chain assembly can be moved. ****MAKE NOT OF WHERE SAID SCREWS/BOLTS ARE BECAUSE YOU WILL NEED TO DRILL HOLES IN THE PVC SO THAT WHEN YOU RE-ATTACH THE CHAIN ASSEMBLY THE BOLTS AND SCREWS SUPPORT THE PVC AND YOUR CHAIN ASSEMBLY, AND
THAT THEY DO SO THAT THE FLAG EASILY INSTALLS****
4. Buy flag material. This is easier said then done but it needs to be extremely water resistant AND resistant to vandals. At my course I'm on my third set of flags but I found some great nearly day glo orange vinyl fabric (it's the stuff that they make tents out off). I found it online for $25 for a 9 yard X 9 yard sheet. I had to cut it to fit the size of flag I wanted but that doesn't take long.
5. You'll need some screws that can hold the fabric up and will prevent vandals from easily tearing them down. I used 1/4 in screws at about 1/2 inch long. They will be at the top of the flag pole and I recommend 5-6 of these screws so that flag stays in place for a long time. If you want to be really anal, rivets could be placed on the flag material so that the screws do hurt the fabric, but the material is not so expensive and we're doing this on a budget.
6. Assemble the flags. I recommend doing this at home before going out to the course an attempting to place them on the basket. You can have all the flag material on the poles, and have the holes drilled in where the screws/bolts will go on the chain assembly and the PVC. Plus you'll be at home and no one will be throwing discs at you while trying to do all the prep at said baskets(hopefully).
7.Install the flags. This step might be the hardest because of things you might have not prepared for (Frozen bolts, frozen screws, etc.) You'll need at least one cordless drill, all necessary drill bits, a pair of vicegrips or adjustable wrenches and plenty of battery time on your drill. The drill is really just to help with the bolts and the screws once they are loosened. I recommend loosening the bolts/screw/nuts with standard tools first to prevent stripping of the threads (remember that the baskets have been in the weather for a long time) A can of WD-40 helps too.
8.Enjoy your results. Expect to replace the flag material every couple of years because of fading and vandals. Vandals also like to completely break off the PVC pole at the base sometimes because they are a**holes, and they need to be flogged for being idiots.
I did this project solo and with all said materials and time I'd say that it cost me about 6 hours + $75 cash. I'm sure it can be done cheaper, but honestly I thought it was worth the investment at my course. Sorry I don't have any more recent photos, or ones with the current flags but here is my course with baskets sporting the first time I did flags: