I have a 20 year old clock with the same movement. I think it has a similar problem to the original poster. It keeps time, but occasionally falls well behind (in a dramatic way -- I think that it may stop for some minutes and then restart). Seems to happen more with semi-depleted battery, but not always.
I too only see the same replacement part listed on ebay -- assume this must be discontinued.
Have you found a correct alternative? If so, can you let us know which model number movement is known to work?