These are the dealers that I personally use and recommend.
You just can not go wrong with this golden list. 

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One of my favorite on-line knife shop sites. They have if not the lowest, then close to the lowest prices on just about all production knives including balisongs. And, the stock what they sell for immediate shipment in most cases and have excellent customer service.

EDC Knives is one of the great supporters of Balisong Knives. They usually have an excellent selection of custom balisongs from a wide variety of makers available. Because most of their inventory is one-of-a-kind custom knives, it's constantly changing.

Bladeart.com is another dealer who always seems to have a few nice balisong knives from various makers in-stock.

New Graham Knives is one of the largest knife retailers on the internet and balisongs are a speciality for them. They have a huge stock so they can often ship immediately. They are well-known for their customer service and their band-aides. And they usually have nearly if not the lowest price on any knife they carry.

If you appreciate fine things, fine art, especially fine knives, you should meet my friend Michael Donato. While he doesn't often have balisongs in-stock, he always has a great selection of other knives... and a few other interesting things from time-to-time.