The light/strong tradeoff is always there, and if it's strong enough to hold the engine safely (which is always the call of the guy under the engine), and it's light enough for whoever is using it to handle it sufficiently, then it's probably good enough.
Here's a pic of the steel braces that Tom Dooley (OffroadSHO) made out of scrap he had laying around. I think they've been used by several people (me included, as shown here) with good success. They're not feather light, but they're not hard to handle, either. They're certainly plenty strong to hold the motor up.
So there's all kinds of ways to solve this problem, and I think plenty of people have had success with Scott's wooden arrangement, the Harbor Freight brace that FAST4DR used, and this sort of steel thing that Tom built. So whether you're handy with wood, metal, or ordering online you should be able to get there from here.
BTW, the red strap clamps are to hold the tranny and allow it to be slowly dropped by one person. This makes a one-man clutch job pretty easy.