Re: need brake help
How about a small parachute?
Seriously though I think you intended to say you want to do away with the coaster brake and SWITCH to hand brakes.
First, I'd leave the coaster brake. You could just remove the brake arm but why not keep it for a back up brake.
You have a couple options for adding rim brakes. You can buy a set of larger caliper brakes made for BMX bikes and mount them through the center holes your fenders mount to. The other option is to find some horseshoe shaped linear pull brake adapters. I've used both these and the linear pull brakes work better. I just can't for the life of me find where I got the adapters. Search the net long enough and I am sure you will find what I am talking about. In either case you may have to modify your fenders by cutting small sections out to allow for brake operations.
In the off chance that you really DO want to get rid of both the coaster AND hand brake options a small parachute is probably your best option.