Magnetic Fill Nipple Cover
If you have clearance issues with your foster style fill port dust cover and your LDC, this magnetic nipple cover will likely solve your problems. It is available for a discount with many of my LDCs, so look for that option if you are shopping for a LDC.
It also works great for the Umarex Gauntlet, much better than what they supply with it. You can reverse the fill nipple, and it'll hold itself to your stock screws while you refill your air rifle.
Before ordering, please make sure your fill nipple is magnetic!