you might also check this out, pretty much the same design (one less op amp), very simple (as the title suggests):
there are a lot of DIY phono pre stages around online if you look. this one is suuuper simple tho with lots of helpful pictures. depending on what you want, i don't find small enclosures to be that expensive; you can get a small aluminum or steel one for under $15 easily on digikey or somewhere. shopping for a rack mount tho starts to cost.