The stuff I bought came from a place called tnutz.com granted I built a really heavy light rack out of it not a stand, but the stuff is strong, like I said you just need to know how to engineer it properly. What that place really excels at discounting is the connectors, one of the nuts for instance might cost 35 cents or 12 cents for the economy ones, versus 80 cents or 20 cents of the "brand name" which doesn't sound like a lot, but the reality is those little screws and nuts and all those fasteners really add up in the long run. The real key is to understand the strength of the material and try not to build the "wood equivalent", for that tank I could see a stand somewhere in the $200 or less range that's perfectly strong enough.
That said, nothing wrong with 2x4s, the slap some 1/8" or 1/4" plywood on the outside, stain/paint whatever. If you don't need to have anything under the tank (i.e. not plumbed to a sump) then you can completely enclose it so no one needs to see 2x4s.
The problem is that a 4' x 2' footprint typically is for a much bigger tank, so any "off the shelf" ideas are going to built as if a 100+ gallon tank is going on there, which you don't need that level of stability. Other options you can possibly do is just bolt two smaller stands together. Just as an example
This stand is 48" x 13" or so, so two of those gives you the footprint. Bolt the legs, screw a sheet of plywood across the whole thing on top, and under, and you got yourself a usable 4' x 2' tank stand. The price isn't super cheap, but I get emails from Petco all the time "save $30 off $100, with free shipping" or something. Granted not saying you should do this, just floating ideas out and something might catch your eye. FYI I use a similar stand for a 40 breeder, I think cost like $20 or $30 from Petco, it has it's issues sure, but it's fine for a tank that small.