Charterguy - the problem with the manufacturers is sometimes they can't supply an item from stock; it can be anything up to 180 days' leadtime.
This is where the "independents" can help out; brokers and stockists, many of whom have inventories purchased as surplus from airlines and manufacturers. The reputable suppliers will only stock items with a proven history; these are, by and large, the more well-established vendors. After all, the aircraft you're flying in is second-hand.
The bad guys are most often sole traders, or companies with one director and 2-3 employees, like the one I used to work for. I left when it became apparent that the director had no interest in where the goods came from, as long as the price was good. I wanted no part of that, told him so, and walked away. I'm very glad I did, as I know he had bought goods from Panaviation in the past.