I checked Cowboom, right now they only have $135 XL's, a couple with a 5 rating (out of 8), which is minor scuffs or scratches, though no charger or stylus, which mine was advertised as and actually had. With shipping tax, it might be $142 or so. Also, Amazon has a couple for $140 plus $6 shipping. Which is very low by amazon standards! I would keep your eye on both of those sites. Also, keep an eye on the auctions at cowboom. I saw it there and just went to buy it now, for the $125, I was like really? The 20 people bidding are gonna run up the price to 125 overnight, I am gonna buy it now, since it was in great condition and the small chance that I could get it maybe 4 dollars cheaper was not worth the risk. I think the auctions allows for the owner to sell, and the store to get a commission, but they seem lower than the store pre-owned prices, which are still very good. So yeah, I'd check it out from time to time.
Let's see, have you tried Craigslist? I find that a good number of people are willing to sell cheaper that Ebay Users or Online Stores since Gamestop has a $60, yes a $60 trade-in value! And Amazon has a $105 trade-in value, but only for an Amazon Gift Card. The point being, people are willing to sell their XL's around $100/$120 if they are really strapped for cash, and they usually have the basic accessories. I am not sure where you are from, but if you live in or near the city, I'd look into it.
Well, I hope this helps. Everyone deserves a 3DS XL in order to witness greatness of the X and Y games. Even us cheapskates :p