I've had good success with StickerMule. They often come in cheaper than the wholesale suppliers such as Stouse, Gill, and Zoo. Of course, they sell direct to the public, so it may be to your advantage just to direct your customers there and let them order themselves (I give them an option of me doing it for them with a 20% markup, which I am completely upfront about).
With easy internet ordering, cheap prices and fast turn-around, a lot of what used to be wholesale trade printing has been lost to direct to the customer sales. With huge volumes and efficient operational set-ups, selling direct is more cost effective for both the printer and the consumer. The wholesale trade printing option, which traditionally involves a trained support staff and personal contact, is burdened with inefficiency which is reflected in the prices they must charge.
There is good and bad here. The bad is that I miss personal service. You used to be just able to pick up the phone and call your guy, and he would take care of all the details. Now you have to painstakingly enter all the details yourself, and talking to a human is probably not going to happen. The good is that prices are lower than ever, and you don't need to call anybody; you just order online what you want yourself (or have an employee do it for you). The younger crowd (under 40 or so) just thinks this is completely natural, and can't imagine why somebody would actually want to "call" a "salesperson" on the "phone". Older people miss the personal contact and the professionalism that was available, but that came at a cost.
As far as making money goes, I gave up years ago trying to mark up commodity products. Your customer is going to see the direct-to-consumer price anyhow with a few clicks of a mouse, and it is an uphill battle trying to get them to spend more than the advertised cost they see on the internet. Even worse is when after the sale, the customers see that they could have bought the same thing off the internet and saved a lot of money. The feel like they were ripped off! The way to make money here is by offering layout and design services.
