Sorry to be back late for the battery questions... yes, the C.R.I.S. adapter works well from everything I've heard, and my OM tech recommends them for those who don't want to modify the cameras.
Other solutions are: Zinc-air hearing aid batteries with o-ring or other spacer. The advantage is the batteries are very cheap and available, even though the life is much shorter than mercury or silver.
Wein zinc-air cells; same as above but the form factor is the same as the mercury cells, so no spacers needed.
Modification of the circuit with diodes to reduce silver cells to the expected 1.35v of the mercury cells. This is what my Olympus tech does with every CLA on the older bodies that take mercury cells. In addition to being the ultimate solution, it means I don't have to have more than one battery type. Getting ALL my old cameras modified would be expensive though since a good CLA is not cheap.