badger ordnance makes this one, i like it. says "front towards enemy"
then there's a few that look like this.
the ones that are out there are generally for rifles with heavy or varmint barrels, so making it will most likely be your best bet
Remington 700P - .308
Norinco SKS - 7.62x39
Mossberg 500 - 12 ga.
Savage FV64 - .22
Marlin Model 60 - .22
EAA Witness P - 9mm
AR15 - 5.56x45
Remington 870 - 12 gauge
"Never let the future disturb you. You will meet it, if you have to, with the same weapons of reason which today arm you against the present." - Marcus Aurelius