There has been so many custom maps over the years that building a full collection with all of them would take quite some time, and some of them has been probably lost forever, and some of them are completely broken or incompatible with today's versions due to outdated props, textures and the spawn system that has changed since. All of the custom maps that I still have (only counting final versions of them) totals to 1.30GB, and I'm pretty sure at least a quarter of them no longer works.
Most custom maps were made before the bots update and they've not been updated since. Some do support bots however such as cy_funhouse and ge_siberia_cc2. You can add bot support yourself in any map with the built-in node system if you wish.
Anyhow, good hunting to ya'.
