Ebay.
Seriously, the chances of getting scammed are exceptionally high. Paypal+Ebay gives you a chance at recompense if it turns out to be a box of pinball machine parts.
Ebay is probably one of the safest places to obtain mining gears, but you pay for the "safety", finding gears in other places would be a lot cheaper, and of course, you pay for it with a chunk of risk, while the majority of miners resllers are scammers, legit sellers are there, one should spend a bit of time trying to source a legit seller rather than paying 30-40% extra just for safe trade.
OP, if you don't mind telling me where are you located, I might be able to recommend trusted sellers in your area/country.