You can buy real, honest to goodness Klein Bottles from Acme Klein Bottles Inc. at! This is a one-man operation by Cliff Stoll (yup that guy).

Don't be discouraged that the webpage looks weird, the klein bottles (or a 3D immersion thereof) really are for sale! He's also selling Klein Hats, Klein Steins, and portraits of Gauss ($10 Deutschmark bills).

Every topologist should have one.