kragen parent
Hardware store, usually. 3.5 digits is common, 4.5 digits less so.
3.5 digit ones sell for far less than that (especially the infamous 830-series based on the ICL7106 and its clones). I haven't found any 4.5 digit ones at that price.
I might be misremembering. How much have you found 4½ digit multimeters to cost?
Around $30 at the very, very least.