I found a clamp on hi viz tube that slips over the barrel and fits in place against the bead. does wonders for old eyes and low light conditions and you can take it off and put it on another gun if you want. Not quite up to the gun with rifle sights or my scoped gun but it beats the plain bead all to heck and gone for me.
This one for a shotgun with a rib.
http://www.midwayusa.com/product/952...ble-lite-pipes
They also have magnetic ones, mine is just a 3/4 ring of plastic that spreads apart and fits over the barrel, sorry I don't remember where I got it but its stood up to a lot of shooting in the last 6 or 7 years.