I still use 2 pairs I made myself years ago! Wooden file/trowel handles, 13mm dowel and 6mm wire eyes from a hardware store, cheap as chips.
The flags I got through the RA, plain red and yellow, but the stiff, old fashioned nylon type, I asked the wife to machine sew some cycle spoke ribbon on to use as ties, this stuff is as strong as wire lol, a couple of quid from a bike shop gives you a metre or so, you only need enough to make 2x150mm ties for each flag through the eye screwed into the dowel, easy to strip and wash, or repair
I still find that when using these for club assistants, you'll probably hear them 'snap' as they're raised nearly as much as you'll clock them in the corner of your eye