What about wiring in a third battery to the remote? Most remotes use two batteries, and LED's work a little higher than their reccomended working voltage. It MAY ruin the remote, but shouldn't. It can be done with no electronic experience, and no soldering. If there is a significant difference, you might be able to notice with a PC cam, or just about any other video camera, since they can view IR frequencies that we can't. You can also use a cam just to see if it is functioning after your rewiring. Insert a piece of thin cardboard, like from a box of cereal between the batteries if possible, otherwise between the battery and the battery contact. A small peice of wire can be inserted on each side of the cardboard with the ends going to the extra battery. I used to use this idea when I was a child and didn't have the correct size batteries for my toys. I wired new batteries on both sides of the dead ones. I know it all might sound silly, but the whole idea here is doing something silly.
Steve
BTW- If you have a small diameter copper pipe (like 1/2"), with the inside still shiny, the IR LED might be more focused if it is shined through the pipe. I know it works with penlight flashlights.