Loopmasters made a bunch for £25, Elektron have quite a few around the same price too - as well as a free one called 'Drum Enthusiast'. I've bought a couple, but find I rarely use them. If you know what kind of sound you are after, there is an absolute shedload of samples out there available for free. As far as I'm concerned, it makes no difference whether they are made 'for octatrack' or not. Octatrack can use any sample to do anything.