Jumps can be made from all different types of materials; from cardboard, to popsicle sticks, or even rolled up newspaper. You can find a tutorial for DIY guinea pig jumps using recycled cardboard material here. You can also find a tutorial for a freestanding agility hoop jump here.
Some guinea pigs enjoy jumping more than others, so don't push your piggy to jump too much if they don't seem to enjoy it. It's a good idea to keep jumps extra low for older or over weight pigs. If you're curious about how high guinea pigs can (or should) jump, check out the How to Teach a Guinea Pig to Jump page and scroll down a bit for some info and tips on the ideal jump height for guinea pigs.