This would be my quick fix - a Pulsar spacer, a 386 cell not to damage the chip feet or LCD with pressure and an old battery clamp to hold everything in place. On top of that I would apply a thin sponge on the caseback so that (once closed) it would hold firmly.
"The first and still only LED watch maniac in the East Block" - www.crazywatches.pl
My pleasure :) You might be better off and cut a battery clamp - an oval piece of metal from a beer can and angle it on the right side so it fits the diameter of the module. You would then be able to slide the clamp between the module and plastic module holder where it should stay in place without much support. Then you would just need to secure it on the left with the hinge on the module. Plenty of options will get you there.
"The first and still only LED watch maniac in the East Block" - www.crazywatches.pl