cut out a piece of plastic from some packaging and hot glue it in place. I've done it several time and it work great.
PPS-SFO Paintball Team:
1st Place-2013 PSP Dallas 10-man Open
1st Place-2013 UWL Dallas Pro
1st Place-2013 UWL Dallas Tacticle
1st Place-2012 UWL Dallas Pro
1st Place-2012 UWL Dallas Tacticle
Most Valuable Team-2013 Pegasus Bridge Scenario