Of course that would depend on the network, as some don't support nickserv/chanserv. You might be better off looking at either the network's website or seeing what info you can get from the help channels. I doubt any of them would just 'give' you a bot, although I could be wrong. Probably the only other way of doing this is via a shell account. As far as I'm aware, it's difficult to get one for free, and those that are
free won't let you use it for IRC bots.
If you are on a network that has chanserv, you could register your channel so that you are the founder. If this is the case, type /msg chanserv help