Sorry I can't help with exactly where to get everything, but it's quite easy to build a sump. Especially if you have limited requirements for it.
I'm hoping/assuming that your stand has some space in it for the sump. The most basic sump would be to get a tank (anything that will fit in the stand) and silicon some baffles (glass or acrylic pieces) into it. Glass pieces are available from OSH, Home Depot, Lowes etc and the same with acrylic pieces. The thin ones are easily cut @ home as well. Silicon should either be 100% aquarium silicon or GE I with no anti-microbial stuff in it. Again, available at HD, Lowes, OSH, etc.
I personally like building a sump vs buying one unless there's a ridiculously good price on it. This is basically because I'm cheap, and building a sump breaks down to:
$5 silicon
$8 (4 @$2) for baffles (I've done it with 3 before and it worked just fine)
$3 for acrylic cutter or glass cutter.
?? a used tank. Since it doesn't have to look pretty, anything free/cheap works fine.
This all just my opinion. If you want me to layout a true DIY for it, just let me know and I'll type one up. BTW, it can get a lot more complicated if you want a space for a skimmer, return pump, fuge, X reactor, etc etc.