Cargo Lamp Conversion

[DT1]

I've been searching for information on converting my cargo light to a third brake light. I found that a lot of members here have done various types of conversions and I was wondering if I could just replace the existing lamp with a bright red led. Of course I'd have to run a wire or two but it seems like this might be the simplest way to do it. I noticed that the existing lamp has two posts and a single filament. Does anyone know what LED lamp is used to replace with?