I know this is an older thread, but I wanted to update it based on my findings. I looked forever to find a better allen wrench for the 380 bg. I keep losing the small allen wrench, and my fat fingers make it damn near impossible to use. I ended up buying one from edsracingproducts online. .035 x 60mm. It kind of looks like a screwdriver. Part # EDS-110236.
This thing works great. It's easy to hold and makes changing the batteries or adjusting the laser a breeze. It was a little pricey, $15.00 shipped, but I guess you get what you pay for. I'm not trying to be a salesman for the company, just something I found and wanted to share with other 380bg owners.