I knocked together a set out of clear fir 2x4's I salvaged a few years ago, but I left them to weather and scavenged them for another project since I wasn't using them. 2x2's fit the stake pockets of the AD series pretty well, I suspect they also fit TF trucks. I just put 2x2 stakes in all 4 pockets, used two 2x4's on each side at an eyeballed height, and attached them to the stakes with deck screws. No measurement involved. I just trimmed the top off the stakes.
If you want to keep the stakes lasting longer, cut the tops so they are shaped like pyramids, then the rain doesn't soak down through the end grain.
If you want something that lasts long, use cedar or redwood lumber.
