You can pick up a decent pair of eBay these days, there is also a site called getcanvasplus which supplies a decent enough pair for a good price, however I much prefer to hand stretch the canvas as I feel as though it always looks better, but that's just personal preference!
I tried that and it really works. I use temporary tacks, not the pins. Althought that gives the best results, I also use center to corner technique on less demanding jobs beacause it is quicker.
