(Notice Pete is the smart one and avoids being beaten by Alex).
Pete's trousers are similar to the other droogs. You may notice that their waist areas tend to be puffy. I am not sure if this is due to the shirt or if there is padding around this area (probably a sexual statement), but I'll know when I get receive my clothes. The pants seem to be made of a poplin material. It is not that easy to find white poplin pants, and I looked at some other materials like linen for ease of shopping, but I settled on a very suitable pair of Ralph Lauren white poplin pants (some of them actually had suspender buttons on them!). While these aren't perfectly screen accurate, they actually look very Kubrick-esque, so much that I think they are acceptable.
These pants are around $85.