If its just standard adapter/cosmetic type inclosure, just pick one up at the store if you can locally, and return it if it doesn't work out. If you just want access to the PS2 I'd recommend networking it in any case. Though buying the special adapter might be pricey, I'm not sure. The newer models have an RJ45 port built in afaik.
Thank-you for the advice, yeah the usb thing is just to connect it to my laptop, I have an old ps2 so I can put it directly into the network adapter :)