I think it is possible i.e. acceptable to say "That's OK for me" in the very context that you originally cited. The sense is clear, and it is not strikingly violating of standard English.
"That's OK with me" also works.
Many people also say "That's OK by me".
It might be useful to note here that all such usages are somewhat informal.
Beryl from Northallerton, Jul 27, 2011