I would recommend popping on OLH and looking, I see used Aristocrat cabinets pop up there every once and a while. Other than that, I don't really know where you can find used ones.
However, my advice would be to not bother getting a used one. Just call Bob and order a new one. There are a plethora of reasons as to why I would recommend that course of action:
1. There is no value buying used on these. When I do see these pop up its at close to retail pricing. The best discounts on these are usually around 20% (occasionally 25%) and there's no warranty on the electronics anymore. A new humidification system alone is $300 and the electronics on older units only last 7-10 years. Most units for sale are around 5-8 years old already. The humidification system could crap out at anytime and now even more of the savings of buying used just went up in smoke. I don't know how long the cooling units last or how much they cost but I would assume its not cheap to replace.Theres no value in buying used when you can just have some patience and buy new, with a warranty on all the electronics still.
2. You can't customize it. While this is obvious, it bears mentioning. One of the nice things about working with Bob is the amount of customization you can add to your cabinet. You can choose what wood you want, you can add extra singles drawers, you can add glass tops and doors and its all new.
3. Finding used units in your vicinity is difficult. As you've already noticed, finding used units is difficult. Finding them in your area is damn near impossible. If you decide to take a roadtrip be sure to include the cost of that in the final price. And you still have risk with that, as you don't know how it was cared for. You could take a long trip just to find out that the unit was stored in the sun and parts of it have faded. I've also seen pictures of units that after closer inspection have scratches. I'm not buying scratched units for only a 20% discount + travel costs.
If, in spite of everything I just said, you do decide to buy used I would like to offer a final piece of advice: DON'T GET IT SHIPPED. You don't know what the unit looks like first hand and on top of that you don't know how somebody will package it, increasing the chances of it getting damaged in shipping. This wouldn't be an issue with Bob as you could simply deny shipping and count on him making it right but you have zero recourse with some guy from the internet and I'm sure anybody with half a brain would tell you its not their problem once it gets boxed up.
