I use an Ullman K-2 mirror on a mag base. I have used that style for years. The articulated joints can also be used to attach to another type of base. The magnet works ok but when covered with variour particles of steel, it doesn't stick well.
http://www.thegangbox.com/p-113-ul-mx-mag-base-inspection-mirror.aspxThe replacement mirrors can be bought in bulk packages of 12 for less thann $1.00 each.
I use them without a cover. I don't weld that well any more and have a hard enough time managing one puddle .The extra puddle caused by placing a clear lens over the mirror is too much of a hassle for me.
The spatter and smoke can be minimized by being aware of the mirror placement. Try to place it above the weld or horizontal to it. Minimize placing it below. A good fan or some type of air movement can help minimize the smoke between you and the weld.
Gerald Austin
weldingclassroom.org