Since you have had no other reply yet, I'll name two that are in your price range, even though I have not tried them personally. From boxmods.net, the Big Brother and Little Sister come in variable volt and 5 volt. And oldgoatmods.com has a couple of box mods in your price range. Both seem to be pretty well considered on the forum. Beyond those, most will be outside of your price range - at least the full kit will. My only 5v mod is a GLV2 from Great Lakes Vapor; and it is a very good mod indeed, but more expensive.