I feel a 6X is entirely too powerful for extreme close range shots he is talking about. If shots of only a couple of yards are being taken I would want a maximum of 2X on the low side. Along with a low focus range, this is a very tall order for $100.
For starters you can look at a Meuller 2-7x32 APV that can adjust down to 7 yds. This parallax setting is fine for any extremely close ranges I have shot critters (mice) at with my various springers.
The Leapers Bug Busters are cheap and can focus down to 3 yds. I do not recommend them at all. I had a fixed power and the glass was terrible. It held zero, but that is the only positive.