http://www.multicraftplastics.com/ in Portland and Eugene, OR sell the Rowmark product line. They stock the 1/16th LaserMax and have a limited selection of other thicknesses and the FlexiBrass/FlexiColor products. Their prices for quarter and full sheets are better than Laserbits and of course you can avoid shipping if you're local.
They also sell all kinds of acrylic sheet by the full sheet (4x8') and in half-square-foot increments. Looks like full sheets would be quite a savings. I haven't worked out how much less they are than Tap Plastics because I'll have to reverse engineer my last Tap receipt.