I'm pretty sure it depends on where you live. Where I live in southern California, at this time of year they come out into the open of my house at night. I have already caught two on the carpet of my living room! Also 5 inches is probably much too high an expectation. A wild caught 3 incher would be incredibly huge in my book, and probably any one else's book in the US. The really large ones are found in the middle east and South Africa, I believe. Outside the house, I have heard of them being found under rocks that are more out in the open, in drier desert areas- but the only ones I have caught were in my house. I did recently see one advertised on the petbugs.com classifieds, so you might look there. I would trade one of mine with you for something, but I have no experience at all in shipping live creatures, and solpugids are really hard to keep alive for long in captivity so I can't imagine trying to ship one.
thanks... we need one or two for some research and ive contacted some suppliers but they all said to call back in another month or so.... some UK stores currently stock them but wont ship overseas, and it seems like no US stores currently carry them