[Coco] Battery-Backed RTCs for CoCo?

[RETRO Innovations]

So, what was the consensus for a replacement RTC?

Re-reading the thread:

  * DS1216 and DS1315 are compatible, but really expensive.
  * They also use the "Phantom Clock" protocol, which Gene says can't be
    used with code that uses IRQs.
  * Most newer RTCs are I2C or SPI, both < $1.00, but they are not
    compatible.

Is compatibility more important than cost, or did something else get 
decided?

Jim