The hard part is finding one that does 1/100th of a second. I have not used one yet. 1 second accuracy was more than adequate for the projects I have done needing RTCs. I have seen the ones up to 1/100th of a second as 14 pin SOIC, 28 pin SDIP, 44 pin etc.

Just do a search on the net or on different manufacturers sites for "RTC 1/100" or "RTC HH:MM:SS:hh".

The cheaper RTCs need a crystal and some caps.
Then there are some that only need a crystal.
And others that have them all in the IC.

Epson use to make some, not sure if the still do or not, Maxim has some and surely there are others.

Cost.. for one with 1 sec. accuracy is less than a couple of dollars, for 1/100 accuracy between 5$-25$.