I feel compelled to plug a sculptor I've been a fan of since college: https://www.bathsheba.com/ https://www.bathsheba.com/ They have a lot of more or less mat

I feel compelled to plug a sculptor I've been a fan of since college: https://www.bathsheba.com/ https://www.bathsheba.com/ They have a lot of more or less mathematically inspired metal sculptures for sale, for instance a functioning Klein bottle opener: https://www.bathsheba.com/math/klein/ https://www.bathsheba.com/math/klein/